I was with an escort a few months back, out in Fairview, black girl - "Honey" I think it was, she agreed to let me video her on my camera phone for an extra €100, as long as she got to see it first, and i agreed to delete it if she wasn't happy with it (ie face shots) ...
I was also with a girl in the infamous "club92" in Malaga this summer where one of the girls was only too happy to let me video her in a room surrounded by mirrors, awesome it was, she insisted on wearing a baseball cap which she just so happened to have with her so that I couldn't take any face shots..
I have mentioned to to a few escort girls recently.. but to no avail.
I think it would be better to find an escort you clicked with, see her a few times.. build a sort of trust with her first.. then bring it up in conversation and hope for the best.. thats my advice.