MTHaslett's idea of using concept art is a good one. I was annoyed to find that I didn't have any hi-res prequel concept art lying around in my SW image archives. I found a photoshoppery that some fan did for Episode II and applied a basic cutout filter to it, played with the color a bit and came up with this (ignore the bars):

http://home.iprimus.com.au/paulgaliazzo/sotds_12_test.jpg

I am sure we can mock up a colorful 70's style poster looking cover. However, I'm afraid my hi-res resources for Ep II aren't as great as III or even I & IV-VI. Anyone care to share some publicity shots or concept art?