Sorry Juber3, tiled background images and forums don't go well together. Forum pages are busy enough as it is, and adding a tiled background image makes it hard.
Plus, add on the fact that a tiled background image would need to be loaded for each page. If it were 3K, for example, it would add almost a second to the load time for every page for dialup users. And, add about 150,000 downloads a month into the mix, and it takes a decent amount of bandwidth just for a pretty background.
There's only 10% of the background showing at any given time anyway, so it wouldn't show up very much.
Sorry,
Mike