I often scan a providers photo and search for content on google. Most times I find out she's legit, but other times I find out a wealth of info that steers me elsewhere. In short, they can and will do the same thing with your pic, and if you're out there, anywhere on the net, (and just about anyone with something to lose is), they've got you. And if you have a bad experience, (minor to you but major to her), your taking quite a gamble.
Just move on. Between here, Er#s, 411, BP, SA, and dozens of other local boards, there are over a 1000 ladies that aren't going to ask you for your pic, (or driver license no#, or S. Security no#, or home address, or work address phone No.#, etc).
Its a ladies right to ask for what ever info makes her comfortable, but remember, its also your right as a client to only give out what ever info you feel comfortable providing................
Think with the head above your shoulders, not with the one below your waist...................