This is what I do...
Create a new Plugin at hook location 'global_start' with the following contents:
PHP Code:
$random_number = rand(1, 4);
$random_banner[1] = 'images/logo1.jpg';
$random_banner[2] = 'images/logo2.jpg';
$random_banner[3] = 'images/logo3.jpg';
$random_banner[4] = 'images/logo4.jpg';
If you want to add a banner, just add a new line, change the variable name (_banner[x]), and then increase the rand(1,4), where 4 is the number of banners you have. If you want to remove a banner, just get rid of the line and then decrease the rand(1,4).
Then edit your 'header' template as follows...
Find:
Code:
$stylevar[titleimage]
Replace with:
Code:
$random_banner[$random_number]