he installed a third party theme that changed the background once installed, bongo im sure can tell you how to change the background , but i can only direct you to a theme
mr grim makes really nice dark themes. find some here Virtual Customs
edit, you beat me again jerry, well done.
i would go with jerrys link for now, as you need to sign up at virtual customs and have at least 10 approved posts before you can download a theme... but well worth it