I think the stickers are great but I think the apparel store selection is a bit bland.
Coming from a background in screenprinting and graphic design, I would suggest:
A) Coming up with some different designs like maybe something hand drawn or just some sort of design maybe featuring a beetle or iconic vw's or vw culture. You can always put your logo on the sleeve.
B) Holding contests in which the forum members can submit their own designs, you select which ones you like and have a forum vote on which ones they like best. Winner gets like $20 dollar gift card and a vwv shirt or something.
C) As far as interface of webstore, it is good but when you first pull up the page all the previews are white. I would suggest changing some of those previews to some other colors you offer for that item so the store
doesn't look so sterile and bland.
Anyway, those are my suggestions
I think overall it's a good webstore I might get me a coffee mug for work