In my own fantasy setting work, I try to mix things up as best I can and make sure things make sense, while providing an identification outlet, particularly since I hope to eventually publish with it.
I have made an effort to establish distinct cultures with the non-human races as well as the various ancestries of humans, all of it being wholly non-mechanical, of course, but for humans I have four "mega-cultures," which roughly correspond to their appearance, but with a great deal of bleed-through due to migrating populations. There are numerous cosmopolitan centers, almost to the point of being a rule once you have a full-sized city, with tribalism being stuck more with, well, tribes. Within them, they range from small, primitive villages, to epic civilizations, from mudhuts to crystal palaces, as it were. The four human cultures run, roughly, as follows:
Culture 1: Tan-skinned and brown-haired, with a broad range and a tendency for freckles and other interesting mottling, this culture formed from an island-hopping, boat-based lifestyle, in temperate to subtropical waters. Their pigmentation is thus in the middle ground, because while they can get a lot of sun exposure at sea, they also have plenty of access to shady island foliage. Their eyes are generally blue, to better handle the glaring blue of the sea.
Culture 2: Pale-skinned but quick to tan, blond but occasionally red-haired, and universally green-eyed, this culture's appearance largely results from the severity of their cultural habits -- the culture is based on a deep self-loathing for their own humanity, which generally leads them to either adopt totem animals, or to worship an ideal along the lines of immortality through petrification. They wear masks, cover their bodies at least in paint, but cloth when they can, and the culture is largely split between jungle-dwelling hunter/gatherers, and those who dwell in stone-carved cities in which they stride around in robes, like something out of the Neverending Story. Their bodies basically just gave up on persistent pigmentation due to the rarity of good and proper sun exposure, and the lack of effect that coloration could have on general survival.
Culture 3: Dark-skinned, dark-haired, eye color tending toward brown but having plenty of variety, this culture dominates the blazing-hot, arid planes and steppes, where horses and minerals are abundant. As a middle finger to the historic spite of the farmer's tan in all cultures, dark skin is a mark of prestige in this culture, because it's proof that you don't spend all your days digging in the mines or covered in armor. It's also associated with the richness of soil and general good health and prosperity, while paleness is associated with bones and death and poverty. Their culture tends to range between ancestor worship and prestige worship, ala Ancient Greece.
Culture 4: Pale-skinned, dark-haired, gray-eyed with that tell-tale almond shape to reduce fog glare, this culture is, quite simply, inspired by those Frazetta pictures of women holding spears while hanging out with large cats. They dwell on a long, foggy coastal area, with their society tending to be more complex as it goes inland and uphill, to where the mists are pierced by their towers. Their pale skin helps get in what sun is available when the fog parts, while their dark hair is vaguely useful for making them more visible in the fog, which is rather useful since their culture tends to rely on spears and halberds -- you don't want to accidentally poke someone in the back of the head. Their culture tends to revolve around patience, due to fishing and having to walk slow carefully to keep from falling into holes, relaxation, and the arts that can survive constant moisture in the air. Scarves of various length are a culture-wide accessory, with various patterns, and are often treated like Scottish tartan patterns, and came about due to the ancient use of netting as an extra layer of clothing for those chilly early morning fishing trips. They also ride large cats, ala He-Man, though they have to feed them red meat to get them big enough - the all-fish diet that commoners give their cats don't get them any bigger than large dogs, leaving the battlecat cavalry in the hands of royals and the rich. Which is just fine because jousting is nasty business on a foggy beach.
Copyright me etc.
And, of course, if a player wants another option for appearance, guess what, daddy wore a mask and momma rode a horse and so yes you can have mocha skin and flaming red hair or whatever else.
It shouldn't be hard to pick out the references to real world cultures there, but nobody could accuse me of pigeon-holing anyone into a niche. The whole "It's like a stereotype of the dark ages near London, but different!" thing doesn't appeal to me unless we're actually playing a game IN London.
