They look bored, they should have brought some hats and pipes and conversed with each other about contemporary events.

a_fine_hat said:
They look bored, they should have brought some hats and pipes and conversed with each other about contemporary events.

Having been in a similar position to both individuals on separate occasions, I can say that the expressions are just about perfect, if atypical.

The bound character is obviously a bit blissed, lips parted, expression drawn in. The 'top' is blushing and has an uncertain expression, likely as a result of inexperience. If I were to tell the story, I'd say that these two are usually in opposite roles. But that's just my two cents worth.