They're drawn in 3D, but it's very nice. It's actually called "Mao Space", I think the author spelled it wrong. You can use Google Translate or Yahoo! Babelfish to translate the page.http://mao.sub.jp/http://translate.google.com/#
This guy not only hosts background, but I think he hosts free games that he made too. He says the materials are from his game and we're free to use it.
In the MENU box, under "special background", click on the japanese letters to read his Terms of Usage.
(If the link doesn't work try google Mao Space and click on the first link that popped up.)