There are many reasons, I suppose, but AMownLawn's post about The Onion reminded me of one of the less-acknowledged perks: the ability to be young enough to get away with being completely unprofessional with your computer desktop but old enough to be trusted inexplicably with the education of other human beings. In the case of my class/officemates and I, we went with pictures from The Onion. It was almost a competition to see who could come up with the picture that disturbed the most officemates/students without the boss forcing the person to change the picture.

Some of my favorites are in the replies.