I looked on here but didn't find the info, though found it on the internet. Thought I'd share with others who want to have random images on their site.
Random image with link embedded in the image, good for advertising:
http://www.javascriptkit.com/script/cut144.shtml
Example (scroll down to the advertisers banner): http://bearfootgold.com/forum/viewtopic.php?f=1&t=34
Random image, no link. This one is a little easier as all you need to do is insert the code into the folder with the images, it does the rest for you:
http://alistapart.com/articles/randomizer/
I tested both with IP and they work fine.