Instructions
Connect your PS3 to your computer using a USB cable and turn it on.
Double-click "Computer" on the desktop, and then click on your PS3 in the "Drives" section. A new window launches.
Right-click any part of the window, select "New" and click "New Folder." Name the folder "Photo" (without quotes).
Double-click the "Photo" folder. Drag your wallpapers into this folder. Close the Photo folder when you finish and disconnect your gaming console from your computer.
Turn on your PS3 and select "Photos" from the main menu on your screen. Click "Memory Stick." You should see the images you uploaded.
Select the image you want to use as your wallpaper and press the "Triangle" button. Select "Set as Wallpaper."