Can you please make a HUGE favor to me please Mike? I need this image to have transparent background and, if you can, please no black borders (I was deleting the black leftovers in Paint but, you see, is not easy without professional image editors and I think you have one :p)
It's found on this page, I'm assuming it should be the same on your wiki. On ours, the part that says background: #ffadc0 url( comes right before the URL address of the image that you want for the background. I created a page with a single URL that shuffles between multiple images for this wiki, I can help you with that if you want yours to do that too.
I had to create a website at zxq.net and use a program called FileZilla to shuffle them. If you just want one image, you don't have to do anything like that, but if you want them to shuffle it's pretty complex.