If you want to have your own design made into a shirt for you,
Create your design
Upload it to Spreadshirt.com
Order some shirts.
There are other good ones, like Zazzle and Cafe Press, but Spreadshirt is the one I like best.
Design it on your computer, go buy a tee and some iron on print paper from AC Moore, print and iron.
http://www.districtlines.com/customize/ here's a link where you can create your own t-shirt. Hope it helps.