If the theme is Star Wars, you already know that there's going to be Jedi, Sith, Slave Leias, Boba Fetts, and storm/clone troopers coming out your ears, so ignore all obvious choices. Your idea is already original, and good, but may not be flashy enough. You could spend some time, money, and creativity to go as one of the lesser known but still recognizable characters, such as Momaw Nadon (Hammerhead) from the Mos Eisley Cantina, Garindan (the spy who followed Luke and Ben to the hangar bay in Mos Eisley, a Wampa from Hoth (now that would take some work), Lobot (Lando's aide de camp) from Cloud City, an Ugnaught from Cloud City, Shmi Skywalker, an Imperial officer, one of the Viceroys of the Trade Federation, even the little "Gonk" power droid that was walking around in the sandcrawler, etc. Or really be someone unique - and go as George Lucas, with a fake beard and wig, glasses, denim pants, and a blue flannel shirt with a pillow underneath for the beer gut. The trick is to find something that will stand out from all the Darths and Obi-Wans bound to be present.