Are you aware of the legendary Ryan's Steakhouse story?
Hell, that thing might be an urban legend, but it's supremely well written and if I was in graphic design, that story alone would probably lead me to thinking that selling signs like this would be a good idea.
If you haven't heard it, a web search for "The Steakhouse incident" (with quotes) or "macaroni beef toilet story" (no quotes) will probably turn up yet another re-hosting of it.