Zupas is one of my favorite places to go eat lunch when I am in Utah. They have fabulous soups, sandwiches and salads.
Their main objective on their Facebook campaign is to promote their business which is a cafe that prides itself on healthy, fresh, made-from-scratch soups, salads, sandwiches, and decadent desserts. I think the presentation principle is a major key when someone is trying to promote food. These pictures display that principle quite well. They are presented in a way that causes me to want to go there (right now actually).
They use red, black and white for their brand colors and their logo. These colors are used in their red bowls and the black and white background of the salad picture. They also do catering and below you can see a picture of their truck with the same branding colors.
I think they also observe human behavior and determine that there is a need for healthy choices in our eating.
This may be stretching it a bit, but I think that they also use the progress principle because they have really improved salads to where people crave the kind of salads that they make. I for one, could eat a salad there every day because of the variety and appeal that they alone have, not to mention their delicious soups and sandwiches.
There is also the expectation principle. As seen in the following pictures, there is an expectation of Zupas being a a good place to enjoy the friendship of others, as well as a good place to work. When I go there I expect to have a good time and enjoy my food. The first time I went there, I ordered a salad/soup combo, but was pleasantly surprised to also get a chocolate covered strawberry, more than I expected.