I say no dress code. Just bring out a car and make that shit bounce. People dont't want to overthink themes these days
Dress appropriately if you want.
edit
Too be fair though, I would prefer at least to avoid the stupid masks/underwear/deadline outfit/purple pasties/ect as Bones mentioned. It's just super distracting in pics.
http://ohsheglows.com/2013/07/19/cumin-lime-black-bean-quinoa-salad-quick-easy/
Sesame oil dressings are also great with quinoa, or try a theme like Greek (feta, lemon, oregano, olives, onions, peppers, artichokes).