cool design. Although photoshop is much easier to create designs, I'd start using illustrator. If you really want to go to print with them, printers usually require illustrator or any vector format. You can send them .psd files, but the resolution has to be realllly high--> large files-> grumpy printers.
also, maybe think about how you would apply this design on shirts with the rays. Do they stop at a point or seem to "bleed" off the front or back?
right on, you're stoked. I actually had a design that went over seams and such, but that then required the printer to print on purchased cloth and then put the shirts together after being printed on.
It looks really cool when the design covers larger areas and goes over seams, buuuuuuut... its more $/shirt and then it turned out the cloth they used wasn't pre-shrunk so all the shirts shrunk... bad times haha
but are you planning on starting a clothing company or something?