Basically, I'm just interested in reinforcing the idea that this is a big, unfamiliar city, and strangers can't just wander around with impunity.
There, that gives me enough to go on.
1) Drunken Revelers: A guild of tradesman is engaged in some bizarre merriment that is half street parade and half religious rite. The parties sober demeanor and failure to wear some sign (a daffodil on ones lapel, a tuft of lambs wool pinned to their hair, etc) offends the burly laborers, and they decide to haze the strangers. This can include forced intoxication, forcing the PC's to pay various homages to a deity particularly in a humiliating fashion, forcing the PC's to sing drinking songs, and invented 'rites' of penance to offend the gullible. Poor diplomacy by the PC's could lead to a brawl, or else a reputation for stupidity and foolishness if the PC's prove too easily bullied. Local authorities will tend to side against the PC's if any violence, particularly lethal ones break out, as the guild is large, prominent, wealthy, and above all local.
2) Lecherous Rake: Someone (male or female) finds a member of the party sexually attractive, and goes out of their way to impress the target of their affections in a creepy aggressive manner. The person is a minor noble, and moderately leveled and capable in some fashion. They are quick to take insult and look for any reason to challenge anyone nearby - particular 'rival suitors' - to a duel. Rebuffing the Rake too publically and strongly leads to long term ill-will and scheming against the party member. Giving in and having a fling likely carries a variety of consequences, depending on DM whim - pregnancy, challenge by jealous rival, person turn out to be already married, person turns out to have considerable baggage (wanted criminal, is a lycanthrope, member of evil cult), person brags widely about their conquest leading to PC having a reputation, rake carries a social disease or transmittable curse, etc.
3) Eager Tout: Party is accosted by a colorful street person who offers to sell his services as a guide to the players. He offers to allow the PC's to over pay to be taken to seen easily found tourist locations (such as the tall temple in the center of town), offers to escort them to the best inns for a small fee, promise to protect the PCs from con-artists and thieves, and offers to negotiate everything from room rates in the inn to the price they pay for horses. The Tout offers to provide or procure various questionable and possibly illegal activities from pit fighting, to betting on dog fights, to prostitutes and narcotics. The Tout offers to pay various mandatory taxes on behalf of the party and avoid legal entanglements the party has mysteriously found itself in, as well as negotiate the bewildering array of petty bribes necessary for daily life in the city. The Tout insists the PC's must buy and wear certain charms, wards, and trinkets to avoid variously bad luck, the plague, offending native deities, or honor the King's birthday. Amazingly, some small percentage of what the Tout says may actually be true, although true or not, the Tout always overcharges for his work and tries to gouge the party out of every copper piece possible. Works best when the party doesn't speak the local language. If the Tout is offended and rebuffed, particularly by a party that does seem over its head (severely lacking in Knowledge skills applicable to geography and customs, language skills, diplomacy skills and the like), the Tout may attempt to pick the parties pockets, or set them up for a mugging by the local thieves guild - which the Tout is undoubtedly a member of.
4) Officious Bureaucrat: The party runs afoul of a local tax collector that insists on collecting any number of taxes from the party - 1 g.p. per bladed weapon in their possession, a 1 s.p. 'horse tax' for each beast of burden, 20 g.p. for a mercenary license, 1 c.p. foreign currency tax for each g.p. the party is carrying, a 1 s.p. entry fee, a 10 g.p. fine for not carrying a passport and stamped visa, a 1 c.p. importation tax on each quart of wine the party is carrying, and so forth. The party has little recourse but to pay unless it has sufficient knowledge of the law to challenge the tax collectors corrupt scheme. Even if they can't be bullied, the party still owes various legitimate taxes. If the party bullies the tax collector, it will certainly lead to local trouble and plots of petty revenge.
4) Make way! Make way!: One or more runaway carts either rolls or is dragged by stampeding animals down the street, threatening to crush the PC's and other bystanders. The cart could have broken away as result of simple negligence, or something could have legitimately startled the animals, or an actual malevolent force is behind the affair. Alternately, the incident may have been caused by two or more spoiled nobles engaged in a race or other reckless hijinks on city streets. Regardless, the PC's must avoid the hazard, and possibly rescue others - which my lead to improved reputation and grateful persons. Depending on the cause and the remedy, the PC's might also make enemies (or friends) of the cart owner, and discover some hint of an underlying problem.
5) How much for the plate glass window/ming vase??: A group of teamsters is transporting something valuable on behalf of a wealthy merchant when an accident happens in the vicinity of the PC's. Regardless of who is really at fault, the teamsters blame the PC's for their lack of attentiveness and insist the PC's pay for the damages. The merchant is inclined to take their side unless the PC's are quite persuasive or can provide contrary witnesses. If the PC's fail to pay up, the teamsters file a civil suit against the strangers.
6) You shouldn't have scene that: The PC's end up witness to some sort of criminal or unpleasant activity that the criminals didn't want exposed. The activity could seem innocuous to the PC's, but the criminals assume the PC's understand some context they might not actually understand. This results in the PC's becoming 'wanted men' for the duration of the stay, and at the very least warned by random thugs to leave town before trouble starts. The activity could be a respected civic leader conducting a scandalous affair (with a young boy, a married woman, a low class prostitute, a revered soldier, a celibate priest, etc.), a group of cultists leaving the catacombs, a thief conducting a transaction with a were-rat, an attempted murder, an illegal duel between representatives of two houses, an important person clandestinely meeting with a banished dissident or heretic, a person paying or receiving a large bribe or black mail money, a priest of an outlawed cult blessing followers, and so forth. The more missing information the PC's have but which the party assumes that they don't, potentially the more interesting this plays out.
7) On your knees, worm: Aristocratic custom turns out to be very different in the city, and the PC's are put in a position where they may inadvertently give offense to someone powerful by failing to respond quickly enough and appropriately enough to the sudden arrival of a rather nasty and unforgiving VIP. The VIP singles out the surprised party member with low enough initiative and failure to declare he falls his knees, doff his cap, and so forth for verbal abuse and humiliation. Failure to abide by these demands humbly enough leads to a judicial flogging and a turn in the pillories. Confrontation leads to a beat down by the aristocrat's guards, and possibly worse trouble down the line. On the other hand, the PC's might be able to bluff or diplomacy their way through the trouble with sufficient grace to earn the respect of either the aristocrat or onlookers (who may have their own reasons for despising the VIP).
8) Beware the dark; it bites: The PC's end up in a deserted part of town with boarded up buildings. A ghouls arm reaches through a gap in a window to grab passer bys. Alternately, parts of town which are safe during the day are much less safe at night.
9) Green or Purple on this Street?: Rival political groups (guilds, noble houses, parliament representatives, religious rivals, or some combination thereof) are in the midst of conflict that frequently erupts into street violence. The party may find itself between two mobs of rioters, witnessing a pitched street battle, or confronted by a group of toughs that would like to know why exactly are you wearing a green shirt or worse just assume you know what that means are a supporter of the Fuller's Guild, voting rights for freehold farmers, the pretender to the crown, or the God of Wells rather than the God of Storms and thus deserve a good kicking and maybe a stab wound or two.
10) Whose the victim here?: The party comes across a potentially violent dispute between two parties - a group of laborers and a young girl they accuse of shoplifting/pickpocketing, a local and a foreign merchant the local believes to be a slave trader, an elf and a human bigot, or an individual being beaten by several men. The party must decide if and how to intervene in a dispute that turns out to be more complicated and harder to resolve than it first appears. For example, while there is no evidence the girl has stolen the thing the laborers accuse her of stealing, its possible she was an accomplice to the more accomplished pick pocket, but the laborers are now deciding that if the girl can't pay back the stolen property than she should pay for it by providing her other assets to the group. The foreign merchant isn't a slave trader, but does own slaves he travelling with, but the slaves if interviewed turn out to be rather less than anxious to leave their masters service as he is of high rank in his own country and as such they are treated better than most. The man getting beaten raped the sister of one of his attackers but the lack legal recourse because he's noble born (but it could turn out this rape was less rape and more neither party wanting to admit to the encounter). And so on and so forth. Jumping in without thinking could lead to embarrassing consequences. Not jumping in at all could lead to someone getting wrongly victimized (or perhaps deservedly depending on your thinking).