So my question is this: what would you expect/want to see in an urban fantasy
Honestly? I want, yet don't expect to see in Urban Fantasy...
an interesting and consistent setting.
"Kitchen sinks" are only good when you do something interesting with them (which usually requires a "meta origin" like e.g. in Gunnerkrigg). Otherwise they make more of mess than is needed at best and no better than
world of warcrack clones at worst. Imageboards try to do generic things every other month, and it descends into boring every time, and rather quickly. Conversely, the craziest attempts at world-building sometimes turn out to be really good.
If you have "Inspired by X" draft, it may be a good start, but only if you add
some twist. With "X meets Y" or "X as Y" - potential varies, but usually you'll need something more if it's not one-shot.
Or even if it's a big one-shot: e.g. "The Tales of the Emperasque" had to hunt down and eat some old memes, but it also deconstructed Deus Ex Machina.
Either way, thinking it all through is even more necessary than in non-interactive fiction, because RPG can test consistency harder than anything else - "just stuff the broken parts under the bed and pretend they're not here" is not an option.
Also, most common mistakes (and some new ideas) are covered in Limyaael's Fantasy Rants - it may be helpful to read, and if not, at least there's a good laugh.