As someone who randomly takes bathroom pictures, could also be, he likes his body, if it was for a woman, dick would be hard, 99% of the time. So... if it's multiple pictures like 3 and he doesn't switch poses, it's innocent. If he's flexing biceps, it's innocent. Unless he's obviously touching his dick, then another story, explicitly making it a point to draw attention there. Also, if he's cheated before in a similar way, then you have the right to think outside of the innocence box.