Header Image

Hello, I am using a theme which employs a random rotating header image that changes every time a visitor comes to the site, clicks a link, or hits refresh. I like the idea but I want to change the pictures to something more appropriate to my subject. I found the php template responsible for the images labeled “header-images.php” with the following code:

<img src=”<?php bloginfo(‘template_url’); ?>/rotating.php?image=<?php echo mt_rand(0,100); ?>”
width=”1020″ alt=”<?php bloginfo(‘name’); ?> Rotating Header Image” title=”<?php bloginfo(‘name’); ?> Random Header Image” />

I checked the normal header php template as well and found nothing that points to a potential source, atleast not to me. No links to websites or anything. Anyone have an idea how this stuff works? Thank you very much.