Any pictures taken in the course of carrying out military service on behalf of the US might automatically be in the public domain for copyright purposes, I think, as the person would be an employee of the US government by definition. I don't know exactly how this plays out for military personnel but I'd imagine you waive a lot of private citizen rights when you set off on a tour of duty.

http://en.wikipedia.org/wiki/Copyright_status_of_work_by_the...