I propose this... refinements/criticism are welcome...
Any new member registering would have to provide a plain-clothes, largely complete of themselves, including face, picture of themselves (both together if a couple) holding a piece of paper with their proposed username and the date on it. Perhaps users would need to re-submit every, say, 3 years. This picture would be retained by SLS ONLY and used as a reference picture should a profile be flagged as fake.
So if you want to set up a single female profile using a pic of a Catherine Zeta-Jones (which I found once), you're going to have to convince Catherine Zeta-Jones to hold up a picture of your fake unicorn profile.
This would do little to stop cheaters, I think, but would probably stop the vast majority of creepy basement dudes posing as hotties to collect pics. It would also stop any prostitutes which used other pictures stolen from the web as their "bait" pictures.