This is Matthew Sweeney.
In his Vinyasa Krama book, in which he creates some of his own Ashtanga-is-for-sissies posture sequences, he writes a brief blurb about "romance postures." Obviously, you're immediately thinking Kama Sutra, but in this case he means "the asana that students fantasize most about accomplishing, particularly when they are inappropriate for you."
He names four postures. I think we'd agree that the four he has chosen are apt for his description. However, before we mention them, let's do a brief, informal survey between those who read this blog (yeah, both of you). What are your four "romance postures?" Now, this doesn't mean that they are postures you can't do...perhaps they were at one time, but you've gotten them and now you can be smug about it. Or, maybe this or that posture miraculously came easily for you, but you still love to do it. Or, we could very well be talking about postures that are still out of reach. They also do not necessarily have to be extreme. An informal Cambridge survey came up with postures like Vrksasana and Chaturanga Dandasana, neither of which would we have anticipated.
We'll give it a week and post Matthew's four next Sunday, 3/1. And if you happen to have the book or know which four he chose, let's not ruin the surprise, eh?
Fair warning: Google Image searches for "romance poses" or "romance postures" will NOT get you what you are looking for; "romance positions" is even worse (or better, depending).
In the meantime, check out this tiny section from one of the sequences in Vinyasa Krama. You may need to view it on its own to get the full flavor.