Sometimes right after the jailbreaking process the Wallpaper feature in iOS 4.x is gone bad,
means that user does not have a choice to choose different picture for each home screen and lockscreen :
But there is one workaround to solve this issue as following :
1. SSH to \System\Library\CoreServices\Springboard.app and edit the file N82AP.plist
(You need plist editor for editing)
2. add this following xml content :
3. Save the file N82AP.plist and respring and enjoy !!