2
xoops allows u to create ad client accounts if you wasn't aware..
go into admin, system block and then select banners..
create an account for yourself..
then u can simply create a new banner, upload whatever banner you want to any folder.. and point the url to the banner you want to use..
if you don't want the default XOOPS banners then delete the ones from the XOOPS client account in the banners section..
hope this helps u more..