Re: We need some ...
Some of the signs I've seen over the years:
Warning whomever is self pleasuring themselves AND leaving behind their magazines that they WILL be caught and severely dealt with;
Warning males that the female toilets are for females only;
A reminder that the urinals aren't meant for shitting in;
A reminder explaining that it's unhygienic to leave your number two on the window shelf...now bearing in mind that said windows were about 8 feet off the ground, it was presumably also a falling risk!
And not in the bathroom, but in the kitchen area, a sign asking people to use the microwave to boil milk, not the kettle.