Hmmm...not sure why but it didn't work.
rileyks.. as I said above.. backgrounds will not work well with all of the themes. I checked and see you are using the default SMF theme. The background will only show up in the header, and the footer, area. It will not showup thoughout the entire forum. Its just the way it is with that theme. If you check my forum out you'll see it shows up for the entire page but Im using the Yabb Theme and it works well for that. It does for some of the others too but as I said, not all.
Doublecheck the code you put in.. make sure you have the "'s and >'s correct.. no misspellings
Im abit busy today and wont be on much to come back and see how it is going for you but please put the code you put in so we can see it and Im sure someone else will be able ot help you out.