Photographers take pictures of what people want to see, and newspapers run pictures of what people want to see. It's true now, it was true then. And people want to see pictures of dead enemy soldiers. They DO NOT want to see pictures of their dead friends and neighbors. Since the battlefield photographers were nearly (?) all Yankees, what would be truly amazing was if there were any photos of dead Yankees. And, yes, the government probably would have come down pretty hard on any papers that did print pictures of their own casualties.