The only conculture of mine that has been deeply thought-out is that of the kamawenõ, the native speakers of Evelēranēl. They are an extra-terrestrial race, with an avian physiology instead of a mammalian one. After countless generations of genetic experimentation (they're more than a little obsessed with 'perfecting' their own DNA, since natural evolution takes too long), they are rather humanoid in appearance. As far as concostumes go, it varies quite a bit depending on preference, profession, and practicality (ooh, alliteration).
For day-to-day life, they wear various outfits made of a synthetic, feather-like material, a custom loaned from ancient times when, having lost most of the feathers on their bodies save for their wings, they began to cover themselves with garments made from lost or discarded feathers, both their own and those of other avian species on their planet. Since then, their technology has improved somewhat. They usually wear skintight, jumpsuit-like outfits of this material, in order to best streamline them for flight. Consider it feathery, flight-resistant nylon. (Bad pun alert: I could call it flylon.)
Their higher government officials wear uniforms made of a thick but loose-fitting material intended to actually impede flight - due to some cultural phenomenon in which those with political power must give up physical power.
They also have ceremonial clothing (which in many cases is made of actual feathers) for use at various events that I could ramble on about for hours. But I will spare you.
As far as ornamentation goes, they never wear large amounts of jewelry or decorations, again - primarily because of streamlining, but smaller trinkets such as bracelets and rings are often seen, and in some cases may act as a literal status symbol, with those of certain professions or social classes bearing particular ornaments. A respected geneticist, for example, may wear a ring in the shape of a double helix. And so on and so forth.
_________________I am a conlanger, a scuba diver, a belly dancer, an introvert, a reader, a writer, a gamer, a Superwholockian, a pianist, a clarinetist, a sailor, a CGI artist, a singer, a dreamer, a wisher, a liar, a hope-er, a pray-er, and a magic-bean-buyer. Who are you?
Edit: Substituted a string instrument for a French interjection.