I'm not sure if I'm willing to motivate why I selected a certain pizza based on an image.
Yes, make a judgment on a single image may turn out to be very hard.. many factors, camera efficiency, POV ....
I experienced this myself, when I realized only when the voting topic was made (and obviously too late) that my pizza was not well contrasting with the background on the picture..
So the pictures of making the pizza could help very much to figure out how it is made, it's quality.. quality of the base/crust ..
* So why not make participants upload a full gallery to image hosting services.. and put the link of the gallery with the final picture on the voting topic !??
just make a couple of rules of posting and that's all !
Friends, who is good at math?
What is the probability that, given 144 pizza options, 5 users from one local section vote for 5 identical pizzas, placing votes in the same order?
You're really monitoring every vote !

Hats off mate, bravo!