Very interesting question realtor.
I don't think there's a clear black or white answer. I would say there are five factors to take into account to help decide whether it could work for you:
1) Are your customers very conservative? Would they consider a phtoto on a card to be too self-promotional or vain?
2) Is there a negative association with having your photo on the card? Here in the UK photo's on business cards are not common so would be looked upon as a bit of a novelty with no negative preconceptions. But if photos on cards are stronly associated with a group that you don't want to be pigeonholed with then it might be worth avoiding (not that there's anything wrong with selling real-estate - it just might not be an appropriate mental connection for everyone's profession)
3) Does it fit with your style? Especially if photos on cards are a bit of a novelty - does novelty fit well with your personal style? If you are a very conservative salesperson selling safe conservative products to safe conservative customers then maybe not.
4) Can you get a good photo done?
5) Unfortunately: how attractive are you? Really, honestly. Research has shown that having your photo on a website or literature can be very helpful if you are good looking. As a minimum we feel more of a connection with the person by seeing their face. And the well-known halo effect also means that good looking people are asumed to be more capable and intelligent - so if you've got it, flaunt it. Sadly, the research also showed that if you're not so good looking, then the picture can count against you.
Personally I hve a caricature on the back of my card. It's quirky, it reflects my personality and personal branding as being a little bit different and able to bring something different to the table, and it's always a good conversation starter.
I fully recognise that some potential customers may see it as being unprofessional, or "just not the done thing" - but the chances are that they are not the sort of people who I wolud end up working with anyway. Whereas the people who feel better about me bcause of the caricature could well be my target customers personality-wise.
Ian