In graffiti-speak, these are known as characters. Characters could be human or animal, or even robotic. They can be borrowed from some other source, or they could be made-up by the graffiti writer. "Classically," characters appear as elements in a larger composition. In this case, the characters are the whole deal. These are by Kid Zoom and are along Rt. 139 in Jersey City, NJ, about a mile west of the Holland Tunnel. If you jump over that wall, you'll fall 70 or 80 feet down into the Erie Cut, aka the Bergen Arches.