Ok, so it is possible to make extra products like this available to your customers using the Self Fulfillment method. You can basically just create any alternate products you like (t-shirt, mugs, CD's) provided of course that you have a lab of your own that can produce the items.
(If you wish you could even create a Digital Download product that you deliver yourself via email in this way.)
Lesson 9 in our Kick Start Guide should cover this for you in some detail (especially from the 4min, 30sec mark)..
Lessons 11 and 12 in the Guide will then help you complete the Catalog and Gallery setup!