[dr_zoidberg]

Yeah, in "Person, individual, someone, somebody, mortal, soul" there's the deeper category "smiler" which contains the categories "smirker" and "simperer". Some of the images are (note: my idea was to link to the images directly, but it isn't loading, so I had to take a screenshot and upload to imgur):

* http://i.imgur.com/Wex6pSR.png

Which I say is pretty much what you'd need to train a net to detect people smiling (amongst other things). Of course, there are some refinements you can make to improve accuracy and presentation of the results. My point was: you should begin with datasets that are readily available, and then improve on need (and if resources are available to justify the investment).