I agree with the above, and also personally I don't like how much downward scrolling is required (i.e. most sites would fit more of the primary information on my screen without me having to scroll).
I would add a couple of things though. Firstly: welcome to the forums!
Second, there is some decent looking design going on, both on the site and the t-shirts. While I agree that product shots are good when you can get them, if you can't for whatever reason (budget for example) I think your graphical mockups look better than most people's.