There's a few apps in the market that allow u to do this. The one i use is called multiple pictures live wallpaper. Its free and very customizable. I love it, highly recommended.
You select which 7 pics you want it to use... It will not be shuttling for the pics and will not select them on its own. You will have to go in settings and select which pics you want it to use and every (up to 7) screen will have different pics.. Hope that helps