I had the exact same problem you're having with the repeating background on the forums page.It took me forever to fix it and I don't remember exactly how I did it. However, I do believe that it isn't controlled by the CSS, but by the Content Containers customization.Here is my code for my content containers. You'll want to use your own border images, and your background images. But it will show you where I put the background images in the code so you know where to put it. You'll also need to make sure your width and height settings are set to whatever your particular border images use.