One central element of my DF Felltower game is that the world is defined as we go.
Players say things off the cuff and they become facts of the world.
Chance elements that come up in play are placed into the world permanently.
Observed facts become parts of a larger tapestry of the world.
In short: I don't write the world then put that into action, we put the action into writing out the game world.
Here are some things that have emerged.
Color Coding - color seems to matter.
Red - the local militia and freelance mercenary forces wear red. Specifically, red shirts. Naturally this is a Star Trek joke at heart. It started because I deployed a few hireling minis I'd painted with burgundy or dark red shirts, and then I started painting new ones to match them. Not all hirelings who come with the party are red-shirted ones, but many are, and it denotes their day job (private guard, guild guard, city guard) or professional background (would-be mercenary.)
Dark Blue - blue is the color of the city of Arras to west, and the mercenary companies that come from that area. specifically, a mix of navy blue and military blue-gray and dutch blue, thanks to my Apple Barrel Colors collections. Why these colors?
Because the mini I painted that was selected as Vryce has blue under his mail, and Vryce's player stated he was a former soldier (specifically, a bidenhander master swordsman, but one who can't handle a shield and thus didn't rate much as a formation fighter). I ended up painting a few more "personality" type minis and some generic soldiery types with the same combo of blue. It stands to reason those guys are probably current or former soldiers, either in the service of a kingdom or Free Company or out on their own.
Garish Mixes - denote the Southern Pirates (on nautical types) or Cashamashians. Because I have some oddly mixed types, mostly pirates. I also have some nightmare mixes of colors on some minis to make them look like they threw together looted gear, but I ended up using them as hirelings from "far Cashamash."
Orcs dress like this too, because they have no taste but they do like bright colors.
Not all people in those colors or mixes fit the description, but many do. Like if I say, "black clad" you think "Ninja" or "Johnny Cash," but it doesn't mean every man in black is Johnny Ninja. But it's a good place to start.
Goblins and Elves Might Be Linked - it's not clear how, but they are. They weren't at first, but then rumors came around saying they were . . . right after one player showed up with a goblin who believed elves and goblins were related. The timing was perfect. So either he's delusional (unlikely), delusional but happens to be right (very likely), or knows something about the origins of goblins (it's possible), but in some way there is a link.
It wasn't planned from the beginning, but it makes sense based on observed facts. I laid all of the groundwork for that to be true, but also enough to make an alternate explanation fit the facts.
And yes, hobgoblins are related to goblins. But they're also very different, in ways that aren't really well explained as of yet.
Lots of Lizardmen - So I basically use the same minis for lizard men no matter one - a mix of Grenadier and old GW plastics. (And their newtman friends are a mix of GW Skinks and RAFM Gilla Worms.) I use these guys for troglodyte-types (lizard men with stinky gas glands), lizard men (nothing special, just tough), swamp lizard men (some minor ability differences to the others), dinomen (not encountered yet), and a few others. So obviously they are all of the same base stock. Why do some have stinky glands, others venomous bites, some just brute strength, etc.? That's a mystery. But clearly they are related, because their minis all look the same.
Not Reptile Men, though. Not that I've allowed one yet, but if they come up, they use RAFM Reptiliad minis. Those I've painted in metallic greens and purples with glittering eyes, much like the snakemen. They may be related, or about as related as green snakes and green lizards are - distantly. But the minis are very different (narrow shouldered, long necks) so they aren't the same as the other grouping.
Crazy Wizards are from Cashamash - Not all of them, since some of the PCs are demonstrably wizards and arguably crazy. But the NPC ones? I keep having them come from, or live in, or have some connection to, the city of Cashamash. There is a real feuding wizard culture there of men, women, and things (although some of the things are also people, and vice-versa) down there. Not the "blow each other up with attack spells" kind. It's the "one up each other" kind. It makes for a place to sell powerful magic items, explains why there are so many cursed items (originally meant as a trap for a rival or a rival's minions), and explains why powerful magical items get bought and then disappear from the campaign.
They are ruled by a Prince, though, who may or may not be a wizard. It doesn't seem like it, though. But Prince Valashkalabash IV does have some money to throw around, and he wants Gram aka Balmung aka The Lost Sword of Vryce Dragonslayer. Ruling over a city full of wizards without being a wizard? Clearly, wizards have a healthy respect for some kind of social order and law. Or he's a figurehead. The first of those is much more interesting, though.
Just some things that have emerged from play.