Template as Background

[Shasta]

I found a template that works perfectly as a background. However, I would like to use the "center in browser" option; but when I do the background template gets centered as well and I am left with white edges.

Any way to load the template as the background? I saw on the forum that paint.net is a great program. Can I go into the "choose background color" pane and make my template a customized color? Do I use the eyedropper or the paint.net?

Thanks.
- Shasta