Zazzle has a promotional widget called the MySpace Merch Booth. It is found on on the Store tab under Promote Your Store To Boost Sales. It gives the customer the ability to design their own products using their own images and text.

When designing my Merch Store, I decided to create template images with the recommended resolution printed on the image. One for T-Shirts, one for key chains and another for posters to make it easier for the customer to create their own products.