Easy black wallpaper: Turn off the flash on your camera, put the camera lens down on your leg or something else that will block *all* light, take a picture and save it.
Instant black wallpaper. Its one of the first things I do when I get a new BB.
Posted from my CrackBerry at wapforums.crackberry.com
I use an all black wallpaper sometimes too. Looks sweet with the stock Precision theme as well. It is awesome on the Tour b/c the device is so black, especially the shiny parts around the screen.