There are some exceptions, but most 4-way stops in my region are an ordinary octagonal "STOP" sign with a small rectangular sign below that says "4 WAY" or sometimes "ALL WAY" (if fewer or more than 4 ways) and in places where confusion is likely (or has occured) the little rectangular one may say "CROSS TRAFFIC DOES NOT STOP."

It can't be denied, of course, that the Frat Rats sometimes steal one or more of the signs to decorate their rooms, but that's only common in "University Towns." And even then mostly just when the football team won a big one and they all got drunk.

John