Wow, I didn't see that option at first.
That's pretty close to what I was thinking. It would be neat to have a generic or selectable icon instead of the icon of the active window, though. And give you the name of the group when you hover over it. So, for my communications group I could set a phone icon and it would say "communications" when I hover over the task bar icon instead of the app name.
This works nicely though, thank you!