[Theme: Mystique] Background don't fill the entire page

In all the pages of my web, the background image fills the entire page. Except in [NSFW site removed]. If you look other pages, there isn’t this problem. Maybe the page is too long? Should I split in two pages? Or can I fix this?

P.S: A few days ago, everything was OK. I don’t touch anything but the problem appears itself

P.S.2: Sorry for my english