I figured it just wouldn't work, but one of the people that works on my site did a simple include (calling a PHP page) and it worked! Like this:
<!--#include file="logo.php3" -->
What it does is rotate a bunch of logos from our logo contest, check it out:
http://www.massassi.net
It rotates the logos from:
http://www.massassi.net/holiday/
The main page is index.shtml, and uses typical shtml includes, execs, and date type commands. Try it and find out!
The server is a slow Cobalt RaQ2 running Red Hat Linux 5.something and an older version of Apache...