Background image problem.. :( please help

Hey im completely new to all this and it may sound like a really stupid question..

I have been trying to change the background picture on my forums but for some reason it wont change.
I add in the picture on the admin panel and the preview shows that it has changed, but when I log back to the forums it still has the old background there
it has been driving me crazy for a couple days now so id be really grateful if someone could tell me how to do it?
the forum address is
http://regret.darkbb.com

thanks in advance for any help

Hello,

Please navigate to Admin CP > Display > colors > CSS
Add this code there and submit...

Code:

body {
background : url(BACKGROUND IMAGE URL HERE) repeat  !important;
}

yay! thank you so much :D
lol thats been bugging me for 2 days now
*so happy*

pity the image doesnt look as good as I thought...
*sighs and continues searching*