This list is the kind of thing to keep around for years until one of them actually happens. Then point out that years ago it was a joke. My favorite of the bunch is this:
THE OFFICE IS NOT YOUR HOMEI like this one because it reminds me of a place I actually worked. There was a night shift that came in and used the same desks as the day shift, so everyone either shared space or just didn't use it. In some cases, the day people would own a desk and keep the night people from personalizing it. As a member of the night shift, it very much looked as though "the office is not your home."
Refrain from bringing toys, food, photographs, music CD's, books, magazines, mugs and other personal belongings with you. Your desk must be kept clean at all times and any unauthorized object found in your individual space after office hours will be thrown away. Not following the dress code previously provided while on office grounds can result in immediate termination of contract.
Meanwhile, here's a real sign that's nearly as bad.