Have you tried altering the background Desktop image? Go to System Preferences from the Apple menu pull down. Then under Personal select Desktop & Screen Saver icon. Then select a different background for Desktop (you may need to click on the Twisty to expand your choices) Under iPhoto you can select a picture.
I looked through my default images (Mountain Lion) I can't find one that matches what you have now. But you could have upgraded from OS-9 and still have some of them still present or added some backgrounds.
Don't forget to check what the Screen Saver settings are.