Alternate angles from trailers, deleted scenes from trailers, novelization, comic book, radio drama etc.
T'bone's star wars universe has a lot of good pics on jedi, plus he has links to gregs rossiter's site which has a lot of them.
I recommend the illustrated edition of return of the Jedi novelization as it has the same storyboard posted on t'bones site that has Luke making his new saber, and of course art of return of the jedi and best of the lucasfilm archives.
Hyperspace has a lot of design concepts for jedi but I don't know if you can use that stuff unless you get permission from lucas and co.
Then there is that interview with Richard Marquand from NPR.
the one unfortunate thing is that the shooting script has never surfaced, The "real" third draft script written by Lucas, only bits and pieces are published in making of return of the jedi, and annotated screenplays.
draft variations article posted here: http://www.starwarz.com/starkiller/writings/draft_variations_roj.htm
revised rough draft posted here: http://www.starwarz.com/starkiller/scripts.htm
pics here: http://www.starwarz.com/tbone/cut_scenes/ep6/
http://www.rossiters.com/swo/rotj_cut.html