I recently downloaded SCI Viewer, a handy program for viewing the resources of Sierra’s many SCI games, and discovered a great deal of art that wasn’t used in many of the games. I’ve put together a little collection of pages documenting some of my more interesting finds, which not only include art and animations, but an occasional audio clip as well. The KQ7 page is the largest, since there is a veritable motherlode of unused backgrounds and sprites in that game (I actually had to split it into two pages).
http://www.sq7.org/akril/sr/SierraResources.html
Enjoy!