This drawing features some silly programmer graffiti despite the serious atmosphere. 

The pigeons with IPoAC (IP over Avian Carriers) is a proposal to carry Internet Protocol (IP) traffic by birds such as homing pigeons as a part of an April fool’s joke.

The 3 square icons next to it says eat, sleep, code.

The ones on the stairs refers to another April fool’s joke that created Error 418. Like Error 404, which means “Not Found”, Error 418 means “I’m a teapot”.