The sad thing is, making a unique architecture/fashion for a setting is probably one of the easiest ways to worldbuild. A good example would be Dune. In House Atreides, everyone dressed in elegant, somewhat futuro-medieval fashion with lighter colors. In House Harkonnen, everyone dressed like they shopped at H.R. Giger's garage sale, on the planet Dune, the Fremen wore suits that conserved their water and protected them from the harsh environment, and the Bene Gesserit dressed like sexy, creepy nuns. In Lynch's version, the architecture and ships were also very distinctive. Suits, houses and vehicles must all be linked to the environment they're made/worn in. The people of those places will also be competing with each other to uphold the fashions of the day. If popular women start wearing bustles, or corsets or start binding their feet, other women will copy them. Important places like the capital cities of Empires will also have a lot of influence on the fashions of the surrounding areas, so people wearing fashions from the opposite side of the globe would be a rarity. Small items, fabrics and bits of artwork might be imported from across the globe and have influence on a dominant culture, but you're very unlikely to find outfits from two totally different cultures together on the street, unless one of the cultures is slowly taking over the other culture.
I guess what I'm saying with all this is that I'm kind of sick of Japanese fantasy games/manga where two kingdoms are next door to each other, and in one, everyone wears kimonos and samurai swords and in the other, everyone dresses like they're from Generic Medieval Setting #275. If they're on floating islands and have had no contact with each other for centuries, I could understand this happening, but if they've been trading/immigrating between each other and speaking the same language for years? No. The worst offender for the "Rummage Sale Fantasy Look" has to be Final Fantasy X. Some of the people in that game wear Japanese style robes, some wear bondage fetish gear, and
Lulu wears something that no one in a tropical locale would even think of wearing, unless they wanted to die of heatstroke within 30 minutes. (Also, is Lulu rich or something? Leather belts, fur, and lace/embroidery have been something that only the very rich could afford in non-industrial societies. The world of FFX is supposed to be one that has specifically eschewed technology apart from rare cases, so there are no factories cranking out these kinds of outfits. So where did Lulu get all of that fancy shit she's wearing on a remote, tropical island?) The fashion of Final Fantasy has always seemed really half-assed to me, and I've always thought that every game was placed in some kind of futuristic magic-tek world specifically so the game designers could put in impossible looking, overdesigned nightmare costumes that are more made to wow an audience, than to relate to the setting they exist in.