Forum:Wikia banner?

I'm here again to ask about a cool feature on Kung Fu Panda Wiki. If you look on the top where the navigation place is, there's not only a wordmark, but a whole picture that spans the entire "banner". Sorta like this:

How did they manage to do this?

Salience72 (talk) 06:48, September 9, 2012 (UTC)
 * You mean this right? They are doing it using a code in their MediaWiki:Wikia.css. 07:27, September 9, 2012 (UTC)