I like Randal's example but I think that's a different problem. He's building a LWP-based browser-like Perl script to go pull just images. That's different than enabling a page in a given browser to refresh its images automagically.

The way I've done this is with JavaScript and timers. There's an example of that here. Probably lots of others ... I'm at best a mediocre JavaScript hacker so I usually just snarf up someone else's examples as starting points. They're all over the web. Just make sure you try it out on different browsers since JavaScript and other dynamic HTML is notoriously browser specific.

The page refresh technique mentioned also works but it's not as slick since the whole page gets refreshed. As much as I dislike JavaScript it does make this sort of thing (just updating the image) look pretty nice. A site I worked on does that on mouse scroll-overs with a pretty nice resulting effect.