So I was adding some stuff to my forum and I wanted to know if there is away to get a banner or do something else to just get the players online.

One thing you could do is use the HTML banner and uncheck show current map and top players. This will still list some basic information about the server, but perhaps this will suit your needs.

If you are a GT Premium user, you will have access to xml feeds for your server which includes one to grab the online players. That would required some sort of programming or a plugin on your part to make it look nice on your website.