My answer was in the post above and will work no matter what country they are pulling them from. The legal would not work though.
Bypassing the semi-difficult code writing above, you could write a simple cron job script the renames each JPG and HTML using it with each execution. Links to your images from off-site would break every time it ran. A friend of mine who is a working pro photographer hired me to do her website and does not need to worry about bandwidth theft. Few want to steal well done wedding photos. On a page of hers there is a JavaScript the loads a different image into a location each time the page loads. JavaScript does not have write access and can't rename files.
This is just to show you that a page that is different every time can still look nice and appear normally.
http://www.dianamichellephotos.com/wedding-photos.html Above is the link to the HTML page I referred to.
The next is a link to the flash page that does the same thing.
http://www.dianamichellephotos.com/wedding-intro.html
(Michael McGowan)