Ever notice how your iPhone reverts to a black background every time you plug it in to charge? Jailbreakers now have the option to continue displaying their lock screen background wallpaper thanks to a tweak called ChargingBackground.
Once installed, iOS will stop displaying the black background behind the green battery meter. You can find the package in Cydia under Sections -> Tweaks or use the Search function to find the title. ChargingBackground is free and has no settings to configure at all.