Customization of Guestbook Templates

Hello.

I've installed the proxy2 guestbook on a few of my sites and I can't seem to figure out how to custumize the pages. I would like to upload my own images to personalize the guestbook and I can't seem to get permission to alter the templates of the guestbook. How do I get granted permission? I know it has something to do with my host, but I just need to get pointed in the right direction because I am totally clueless when it comes this.