Those of you on OS 10.2+ just got a nice headless app approved. ToySoft has updated their Wallpaper Changer app to be headless on OS 10.2. This means you can have the wallpaper change every set amount of time and NOT have the app run as an active frame. This is due to triggers that BlackBerry allows devs to set from what I can tell.
Check out Wallpaper Changer for $0.99 in BlackBerry World. Hopefully more headless apps come!