Here's a sign that hangs on our door at work (below). Anyone else who works in a high-rise office building can sympathize with my motivations for creating this thing.
I actually at one point considered starting a little business making offshoots of the concept. The company was going to be called "Solicitors Will Be, Inc." (www.solicitorswillbe.com), with multiple signs available... "Solicitors will be fed to wild animals", etc. Witn little pictures to match. I couldn't cost-justify it, though.
Years ago in the Los Angeles area the Lotus club held their autocrosses at Lion Country Safari, all around the facility on the fences they had signs that said "Trespassers will be Eaten" but I don't think they were kidding!