You can add a background image using the appproriate CSS, however there is a check in place right now that makes sure you don’t link to other servers or image hosts. Basically what I’m afraid of is people hotlinking to other sites, or using an image host that might delete the image a month down the line.

You’re free to use any of the background images you see as part of the site already, although I know that’s somewhat of a cop-out Log in to see images!

Here’s an example of how you’d set the background image for a forum (this uses the troll background which doesn’t really tile properly, but it’s the same idea)

#forum {
  background-image: url(/images/header/background-troll.jpg)
}

In the future I’ll almost certainly implement some kind of file upload system for ForumBuildr, where you can upload avatars for enemies and other bumets for your style (such as background images), but I’ve got to implement a quota for that so it won’t be done right away.