Some beta/prototype screenshots of Super Famicom - Dragon Quest VI from EGM #64, November 1994, page 86. How different is this from the final game released in 1995 ?
http://www.unseen64.net/2009/05/30/dragon-quest-vi-6-snes-beta/ For those interested in the making of DQVI I suggest the following page from Chris Covell website: http://www.chrismcovell.com/secret/weekly/How_Games_Are_Made_DQVI.html
I've seen that book on the making of DQVI on Chris Covell's site. It's really good, and so good of Chris to have the translation.
Not really prototype content, I think, but V-jump released a VHS tape at one point that contained gameplay footage, developer messages, and bla bla bla. I've got an old and shaky upload of it on my server, from when I was experimenting with doing a video streaming archive for these sorts of things ages ago; here Got a much higher quality rip of my own tape on a drive collecting dust somewhere, just waiting for someone with a proven history of quality translations to take on the task so I can whip together some subs and just slam it onto YouTube and whatever.