I'm sure you have already considered this... but just in case.
Here are a couple of links to example scripts:
I love the front page photo's and I think it would be neat to see a random photo everytime I visit!
P.S. The script samples I provided make you "hardcode" which photo's you want to randomly change right in the script. I'm sure there's probably one out there that would let you specify a directory to pull the photo's from as well.