It honestly depends on what the shirt is trying to say. Products, groups, etc, small logo offset on the front and larger design on the back is the norm, but if you're trying to say something or be funny, etc then the front is the way to go. Concert T's usually had logos/design on the front with some on both sides. As someone who collected T's when I was touring the country playing music, I've seen them all ways. I have Ames Bros shirts and they mostly have the design on the front. When I was a gigging musician I actually preferred the logo or design on the front because my hair was so long that it covered the back completely.