cade, I apologize, but Zenphoto doesn't support adding extra data fields without considerable modification, and unfortunately we don't have the resources to help everyone with their customizations. As I said, you will have to be very proficient at PHP and programming to do that.
As Acrylian suggested, I would use tags if you want to group your images. I don't understand what you're trying to do, but that's the best way to group things together.
Perhaps we will have more ideas if you tell us exactly what you're trying to accomplish.