So long as it fits within the theme of the pool, I don't see why not. For the example you given, my impression is the pool is specifically meant to feature the, well, asses of women. At the very least, I've never heard the phrase used to describe a man's ass, so I would imagine putting a picture of a guy in that pool wouldn't quite fit. On the other hand, if a man were to have, say, "beautiful hair," then by all means.
