SilverWook said:
The Revenge poster is perfect for the back cover. Never seen that variant of the 1985 poster art before. I think these two are more iconic though...
http://www.theforce.net/collecting/posters/rotj/style-a.asp
http://www.theforce.net/collecting/posters/rotj/style-b.asp
I don't know if textless versions are out there.
The front cover is from 1983 (UK Quads). 1985 re-release poster is this one.
I posted a good textless style B here. The style A half-sheet could be made into a textless version, as the text is on the left and the artwork on the right.