If you have a nice webserver such as apache for example it will allow you to Alias locations, that means, if you say in your httpd.conf or in an .htacces file:

Alias /images /cgi-bin/image_handler.cgi
[download]

_all_ requests for http://your.domain.com/images/* on your server will be directed to the named script and the part of the request that looks like a path for a user is passed as query string to your script, and then you have to send the correct MIME type header before starting the data output.
As nearly about always merlyn already wrote a column about that. :-)
Have a nice day
All decision is left to your taste