I just wanted to recomend this site: http://malesubmissionart.com/
Over the few years it's excisted, it's gather a LARGE amount of pictures that all in some way display the human male submitting. There are both gay and heterosexual pictures, both photos and painting/drawings. All the pictures come with an explanation for why they have been chosen, and I love reading the different takes on what male submission can be.
If you enjoy male submission, you'll love this site. :)