They had a number of costumes on display - especially from the original three movies -
Han Solo, in all his glory. It was fun to see all the detailing - there were metal boxes on his belt - what they heck were they supposed to be for? they don't open. Lots of pockets (also not used) in the vest. Riding gloves, scuffed boots, embroidered stripe down the side of the pants - fun.
The Princess Leia mannikin and outfit was *tiny* (as I'm sure Carrie Fisher was at that point). It was also amazingly simple - so credos to Fisher for how well she wore it! R2 was awesome.
The iconic Vader outfit! There were pictures of Samurai warrior outfits, which were the inspiration for the flared helmet and cape and some of the detailing. (There were also inexplicable parts - they look cool on screen I guess...?)
Yoda and Obi Wan (and the testing droid). The incredible details on Yoda were lifelike and convincing.
Probably my favorite costumes though were from these nearly incidental characters from the very first movie. At the time, they were so incredibly novel (shadowed monk hoods? glowy eyes??)-
-and reading about the decision making behind the Sand People outfits (they couldn't decide what they should actually look like, and in covering them completely, your imagination can come up with something way better than they could really show on screen) was fun. All those metal thingys on their head-pieces - eerie and memorable for sure!