Just managed to get the template converted to a format usable by me (I don't own Photoshop) and I started putting my shirt together. If I were to buy a GE:S shirt, I would want it to look like this:
Simple so far, I'll try to add some "007" and Moddb stuff to it later. Maybe some awards things.
I like to keep my fan shirts small and simple, (Like the HL2DM and the CSS shirts), I would personally feel kinda self-conscious walking outside with a massive logo going around my front, side, and back.