What you are actually trying to insert is a PERL script which is like a program, not an image. That is why it didn't work when you used the IMG tag to try to display it. It appears as an image on a web site because the script creates the image every time it executes. I don't believe that the DIS boards are set up to allow scripts like the one you are trying to put in your signature.
Maybe if one of the moderators sees this thread they can either verify this or tell us that I'm wrong and then they could tell you how to accomplish it.
Even if it could be done, you need to be very careful of the kinds of scripts that you would try to place in a post or especially in your signature. That is why I don't think that the board will allow these scripts since the wrong kinds of scripts can mess things up pretty badly.