Have you tried to contact the developers who worked on the site? They have a link at the bottom of the page. Click Here
Google has a tutorial that explains how to use their maps. Once you create a new map you can click the location you want to edit, click the icon symbol in the top-right of the location pop-up. Follow the instructions in the pop-up dialog.
You will have to upload your own gif to your site or somewhere else on the interweb, so you can access the URL.