I'm always intrigued by the sometimes blurry dividing line between what is obscene and what is not. In the picture below, the lad's junk is not patently visible. It's obscured by the sheet.
We don't actually know for certain what's causing the sheet to stand up like that, although we all have a very good idea. It might not be his junk. He could be perfectly flaccid and that's just a prosthetic of some sort.
So the obscenity is not explicit in our eyes but it is in our mind. We presume he has a hard cock. We start to concoct erotic stories in our minds -- he's awakened alone on his day off and can't stop thinking about sex. Or he's anticipating his lover crawling into bed in a few minutes. Or he's watching some scorching hot porn on a video screen beyond the frame of this image.
But still -- is the picture obscene in and of itself? Is a photo of a man who might have an erection as obscene as a photo of a man who clearly has his cock fully exposed for all to see? If you put the latter on the cover of a newspaper, people would howl with outrage about the obscenity. But what if you selected the "covered" one -- is that any less objectionable and, if so, why?