Funny that you posed this question when you did. A few weeks ago I ran across an enticing escort ad, but one of the pictures looked familiar. The next day, I was looking at a dudesnude profile and there was the same picture. The dudesnude guy is not an escort. I've chatted with him in the past and know that it is his, not the escort's, picture. So, I told him. He contacted the escort and that picture is now gone.
In answer to your question, if you hire a guy and he does not match his pictures, turn him away and tell him why you are doing so. If enough people do that, he will either post current/accurate/his own pictures or find a different line of work. Aside from that, I suppose we could all send e-mails to the guy calling him on his fake pics.