Porn on the walls is going a bit far, especially for 2008.
I'm talking more about the tone of jokes (non-individually directed) and things like that. Stuff that you don't need to remember to hide when clients or the Board of Directors come to the office, and that doesn't turn up in an email log that will be reviewed later on by regulators. Stuff that you can switch off right away when you need to go in to "serious professional mode".