I can't say that I would buy it as it is. I think the soldier would look better filled in, and the outlined box seems unnecessary. Also, I think smaller and multiple soldiers would work better than one bigger one.
As for colors, I would suggest a yellow shirt with the color of the darkest shirt for the actual design.
I don't really like it in the box in the center...I think it would be cooler if you made it a graphic on the sleeve with something else on the front, or just take away the box and put the graphic in the bottom corner of the shirt.
I like the box, as it hearkens to the keys used to illustrate ammenities on tourist's maps. This one would probably signal that "yes! there /can/ find American occupation here!"
If the box has to go, of course, it will just look like a lone soldier on a sandy expanse. Which is sort of topical/funny as well.