Really? The Snape/Lupin one? Actually, that's one of my faves, too. They're cute together. (In defense of Remus and Ravenica, that was one of the first pieces of fan art I ever did, and it makes me cringe to look at it.)
And hey, what's wrong with a little wild sex every now and then? (Are we allowed to talk about this on this forum?)
I actually did the Snape/Lupin picture for one of my friends, who writes that pairing. It was months before I actually got around to drawing it, but I think it turned out well.