Instructions
Power on your PlayStation 3 and navigate to your photo library from the Main Menu via the Camera icon labeled "Photo."
Determine which image you want to use for your new background and press the "Triangle" button.
Select "View" from the list of options and press the "Triangle" button again.
Highlight the "Set as Wallpaper" option and press the "X" button.
Press "X" again to set the Wallpaper after adjusting its size on the screen.
Select "Yes" once prompted about overwriting your existing background.