Uniforms. Uniforms?
The unk_4 in an entity's uniform data seems to be the "role" id that either says what it's linked to or determines the pieces. There's at least four types that I've seen.
Type 0 occurs all over the place, mostly entities centered around proc-gen lords and forced administrators of all races. Hoods, cloaks or both, at least one decorated with the civ symbol. Capes can also be used where available, but robes and dresses don't seem eligible. The materials aren't restricted, but the items may be limited to certain specific colors which are always available in dye form to the parent civ.
Types 1 and 2 I've seen only associated with religious sites. They're similar to above.
Type 3 is the most common one, seen usually with the actual human/dwarven kingdoms, but never with elves. They consist of the highest ARMORLEVEL stuff available, usually breastplates and helmets. One or both garments have the civ symbol. They don't have an armorlevel requirement per se, but they're always restricted to "material_class = 16" (Armor).
e: welp, found one right off the bat. Sure enough, they're outfitted with helmets and mail shirts.