I work for The Guitar Shed. We operate music stores on military installations. We currently have stores at Keesler Air Force Base in Biloxi, MS, and also at Naval Air Station - Pennsacola in Florida.
We have a partner vendor on base at Keesler, who has just acquired a Direct-To-Fabric printer.
Through him, we are able to offer high-quality custom printed shirts, with any image you submit. The higher resolution the image, the better the shirt will look. A higher resolution also means we can enlarge the picture more.
This printer produces a super high quality product. This is not your common screen-printed shirt that will fade & peel after a few rounds through the laundry. Another benefit of direct-to-fabric printing, is that you can get 1 or 2 shirts -- you don't have to order a dozen or more.
Several colors of shirts are available, but personally I think black shirts look best. Sizes are S - XL, with 2X and 3X available soon.
Prices are:
Shirt with image on Front or Back: $24.99
Shirt with image on Front AND Back: $34.99
USPS Flat Rate Priority Shipping $5.95
The shirt pictured, was made with simply an image I saved from a steel guitar website.

Close up of the image on shirt:
