It's usually too expensive to print a hundred or even a couple dozen shirts to test market every merchandise design and idea. But using print on demand services like Zazzle, Cafe Press. Printfection and Spreadshirt allow you to test market them at no cost. (This Sguidoo article offers some comparisons between the services.)
Upload any image or use ther online design tools, pick the product and cost and put them up for sale. You can link from your site or better yet grab the image of the product, place it in your own online store and see if sales roll in. If just a few people buy have the on demand service fullfill the orders and drop the product. If you're happy with the test order a quantity free from your usual sources and ship them out yourself at a higher profit. (This article offers some comparisons between the services.)



