I don't really care what's on the t-shirt as long as it isn't white. :)
But, here's an idea. On front: A jar of peanut butter, and a jar of jelly. On back: a sandwich.
AdminKit Plummer (Organizer, DevOpsDays) commented
So, here's my idea in graphic form. I'm not designer so hopefully the gist of the concept comes across.
Dev is Jelly, Ops is Peanut Butter ... and the rest.