[Fraik]

Well, if its anything like I think you mean, here's how I did it:

1: Make a background picture thats just a few px high but as wide as your forum is including the graphic borders
2: Create a new div class in your css file, make sure to give it a background and width property
3: Open the new div class in your header, and then close it in your footer.

Here's how the class is defined in my CSS:

.bg {
background-image: url(images/gradients/forumbg.jpg);
align: center;
margin: 0px auto;
width: 985px;
}