Background Doesn't Show

When I try changing the background to an image it works in the admin panel and shows up in previews of the website. But when I go back to the site, the old backgrond keeps showing up! Why??

Have you waiting at least 2 - 3 days?
Also, try resynchronizing your forum.

Yes i have, and i have no clue how to do that

1. Administration Panel
   
2. General tab
   
3. Forum -- Configuration
   
4. Scroll down and you'll see it

Resynching your forum will do no harm to your forum; it just relinquishes some minor issues with your settings.

I tried doing that, and I added the background again, waited days and still nothing >.> It's not that I absouloutly [sp?] hate the background, it just doesn't go with my site really.