My twin told me about this great new app from cydia called "Desktop/SMS Background" on the iSpazio repo. This free app lets you change your SMS or home screen wallpaper on the fly without the use of Winterboard or SSH! OS 3.x.x+ only! It's easy to do. Just install it, and then go into your wallpaper settings on the Settings App. Then when you click on an image. Click on the "!" on the left to Set it as the SMS background, or choose the "!" on the right to choose the springboard wallpaper! Even better there is no respring needed! Enjoy.