@optimus. I have created a Vbulletin plugin, check out http://www.besthostingforums.com/showthread.php?p=83623.
It will be good that you should create a banner add too(800*90), so it load much faster.. Also your site was down in the noon time, so it will also affect our forum, coz our site will only load after all the php code gets loaded..

Edit: i also used your text php code, and its loading time is same as the image code..
http://www.warezsoul.org/add2.php

suggestion:you can create a xml flash banner, its really simple but you need to update the images every week..