This old grouch has serious mental reservations about the commission of graffiti. The few clever ones do not atone for the atrocity of the desecration of the environment by the stupid ones. My favorite uncle said:

"His ambition is very small who writes his name on the shithouse wall".

I did see one appropriate one in latrine in Harvard lecture hall. Some s.o.b. had actually stood on the seat to relieve himself, not trusting well sanitized seat, leaving marks of soles and heels visible. The next occupant wrote on the wall avove it : "You might as well sit on the seat, the crabs in here jump 15 feet."