Each site can have its own Header Image. (This site doesn’t have one, but you can see an example on the Rules Tip Blog if you want.)
You are welcome to create your own, or ask the Graphic Design Gang for some help.
Whatever you do, please try to avoid using the default images that come with your theme. 🙂
We strongly recommend using the Magic Judge logo in your header to help brand it as an official Magic Judge blog.