I've scanned the largest versions of your favorite posters, and a few obscure ones too.
http://orangecow.org/starwars/SWposterbook/
Go ahead - download 'em all. Make covers out of 'em. Some of them are "detail" images that only show the main part of the image, zoomed in, which is nice because you can combine that with a less detailed scan of the whole thing to get a realllly sharp image.
You don't deserve me.