This is a small application volDeus is developing and will evolve into a full-fledged skin editor for Spb Mobile Shell 3. At the moment it only has the ability to change panel backgrounds (among some other helpful tool options), but it has a decent GUI and is unique in that it does not overwrite any changes that have previously been made to your copy of MS3 by other skins or widget packs.

http://forum.xda-developers.com/showthread.php?t=523329