IMAX film is square, not rectangular, so I don't think it would work well with any OT restoration projects in the widescreen format. The footage would be great to have though.
The sequence was reframed, with different effects, for the IMAX version. From
http://www.dga.org/news/mag_archives/v21-3/efx.html:
"Actually, the special effects sequence during the Star Wars segment of the film was created by Industrial Light & Magic, part of George Lucas' family, especially for the IMAX movie."
Here's a site with some small screenshots from "Special Effects" :http://www.agraphafx.com/StarNet/Newstuff/imax.html
I can't find any bigger images, but I bet they would make great desktop wallpaper.
Edit: Fixed first link.