You know to catter to them why not just add 2 fields? 1 for just the banner image name which is in $home/images/banner, then and advanced option to allow for HTML to be placed there instead. Then you guys can install some free banner rotating script (
www.hotscripts.com).
If the basic field is empty ignre, if advnaced field is empty ignore.
Just some suggestions, I will try and edit this for you guys!