Everything has been used from linen to cotton velour to roughspun wool to silk tussah to cordcloth to loden to...
About the only requirement to "fit into the Star Wars universe", by precedent, is natural fibers in "non-Earth-y" patterns. Like... WWI and WWII vintage cotton web belts? Cool. Viet Nam era and later nylon? No. (There are exceptions to everything -- there was nylon strapping on the frames they used for Boba's rocketpack, and they didn't remove/replace them... but the straps were entirely hidden by the flak vest). They've used cotton and wool blends, and Boba's flak vest was a synthetic coated twill -- but they all still looked like the natural fibers they were standing in for, by and large. Nylon was used in a few places, but it didn't really stand out, except when Luke's Hoth Snowspeeder parka got wet on Dagobah.
That's one of the things about the Sequel Trilogy and Rogue One that irks a few of the costumers -- nylon flight suits versus the cotton of the originals. Tends to make them look too contemporary, rather than timeless.
So I'd say check out wool or cotton broadcloth or melton, ask International Silks & Woolens down in L.A. to send you some samples of their heavier-weight fabrics to flip through, get ahold of Brandon Alinger's book on the Original Trilogy costumes, or Trish Biggar's on the Prequels' costumes, and see what sorts of things were used where.