A dozen of sounds from Chewbacca like Arrrghh or Whoa, which are great for customized notifications. The app is free and not official so download it while you can.
As the name says, this app is a widget. You can have a Droid background on your phone and listen droid sounds when clicking on the Droid.
For a couple of bucks this app can be purchased from Play Store. Not surprisingly, it will set a Darth Vader Ringtone as default.
Ok, this is a game and not a ringtone or theme. But. Since this is an official app, you will hear the most authentic Star Wars sounds here. And these sounds can be captured and converted to ringtones anyway. Not to mention that the game is fantastic and addictive.
Alternatively, if you have your own Star Wars sound, you can always use Ringdroid to create a unique ringtone.