Just over a year to the day almost. Why
necropost in a year old thread with an unrelated post?
Z10 - Press both volume keys at the same time to take a screenshot of your BlackBerry. You can also search App World for Wallpaper applications. This one looks like it will let you take a screenshot and make it a wallpaper on your device.
BlackBerry World - Wallpaper
Of course, you could always hit both volume keys and then view the picture (In Media) and choose Set As....Wallpaper. It will amount to the same thing.