[Thelonius Beck]

Originally Posted by Warlord

Actually I was just inserting the code in the little box next to the Standard CSS Attributes under Page Background but that didn't work either.

Then I noticed that the css selector was called .page so I tried adding the following code to the Additional CSS Options all the way at the bottom of the screen but it didn't work either.

.page
{
background-image: url('http://www.projectfanboy.com/vb/images/skins/superman_bg.jpg');
background-attachment: 
fixed;
}

What am I doing wrong?

Your URL is invalid. Therefore, no image will be displayed.
Try it like this.

.page
{
background-image: url('http://www.projectfanboy.com/images/skins/superman_bg.jpg');
background-attachment: 
fixed;
}