Heres a simple un-tested script that will produce a random image on page load, stick this anywhere on a new line in your phpinclude_start template and see what it dose for you.
// # Brad's random banners
// get a number between 1 and 4
$image_id = rand(1,4);
// we got a id, now figure out the name of the image
switch($image_id)
{
// if the random number is one display
case '1':
$banner_name = 'banner1';
break;
// or if two is the scripts thing
case '2':
$banner_name = 'banner2';
break;
// Mabey it prefers three
case '3':
$banner_name = 'banner3';
break;
// Must be four...
case '4':
$banner_name = 'banner4';
break;
// The script could'nt generate a random number for some reason, so we wil use this fail safe image
default:
$banner_name = 'banner_failsafe';
break;
}
// end banner generator
Now you just type the normal html in the header template (or where ever else you want, as long as the script is using vBulletin's global.php). But you will use $banner_name in place of the image name. So <img src="banner.gif"> would become <img src="$banner_name.gif">
Also remember you will need to edit $banner_name (all 5 times it appers) in the php code to match the image names of your banners. There are 5 because the last one is a fail safe, incase for some reason php can not produce a random number but can still display the rest of the page.