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.
The green battery fill meter is not affected by this tweak, it simply appears in front of whatever lock screen background you have already set up. The tweak comes to us from MPow on the BigBoss repository. Once the package is installed, simply respring and the battery charging screen will reflect the change. To revert back to the black background when charging, you can remove the package in Cydia under Manage -> Packages.