...I almost could make the same case for uniforms from the 18th century British navy since Roddenberry also cited the Hornblower series as an influence as well, but those would be pretty out there to expect a bridge crew to wear.
They wear them in one of the movies don't they? Whilst on the holodeck, and then actually appear on deck with them?
That would be pretty fun to have, I think! Especially since there's a lot of space opera where the characters basically do wear naval getups with little tweaks.
Also, I'm sure this has been mentioned somewhere else, but it would be pretty neat to have some robotic costume parts, so you could make a character appear like a robot or cyborg.
If I had my druthers, I'd love for them to be very sort of 'asimov' looking. Something that looks like it was designed in the "golden age" of science fiction, the same way Data's brain often looked like it was from the cover of an Asimov novel.