Instructions
Navigate to the "Settings" category on the PlayStation 3 main menu.
Select "Theme Settings," located near the top of the list.
Select "Theme," followed by any theme installed on your PlayStation 3. Customizing a pre-existing theme allows you to have a custom button layout.
Select "Wallpaper," followed by the wallpaper you want to use instead of the theme's default. Press "O" twice to save your changes and return to the main menu.