It seems animated .png images do not get animated through the randomizer. If they are viewed without the "handler.aspx" or "imgtransfertest.aspx" things though, they are animated properly (the links in the list of URLs when editing a randomizer).
Hi, do you have an example that I can take a look at? Perhaps I can get this to work
In the mean time you might want to try hosting it elsewhere such as tinypic then placing the URL in the randomizer (that will force the handler to redirect it, passing the image directly to the browser)