One of the things you have to get when you go to a convention, is a convention T-Shirt. I managed to get shirts for every year I attended except the first convention. Here's breif rundown of the shirts I did managed to get.
The shirt from GaryCon II is the only one I have that has artwork prominently on the front and back. Basic black, a gamer cliche if there ever was one. I believe the one from GaryCon I was white. Overall it's your basic con shirt with the name of the convention, the date and a nice statement about what it's all about.
The GaryCon III shirts moved the front artwork to the upper right part of the chest and saved the main artwork (by Jeff Easley) to the back. The knight on the chest appears to be the same one from GaryCon II, only facing the other direction. The slogan has also changed from "Celebrating the Memory of the Father of Role-Playing Games" to "Celebrating a Life Well Played". This style would continue into the next year.
No idea what the short for GaryCon V will look like. But I hope it will live up to last year's offering. We'll just have to wait and see.