I've been pondering office space quite a bit of late (OK, insert obligatory television show joke, I'll wait.) (Done?)
My office would be best described as sparse. I've put up a few posters. Hey, I'm a woman, I reserve the right to love Monet's water lillies. They liven things up a bit, but the office is still pretty sterile. My office-mate took a different approach. Her desk and "general area" are full of pictures of her kids, her dog, her husband, etc. It makes the place look lived in, but I'm not sure how much personal information I want to share in this fashion.
I got to thinking today about decor - one prof has an office so cluttered he can't use it. There's space for two people and not much more - and I do think that he does it on purpose, as part of his image, self-presentation, etc. Another one hung up a 1960s psychadelic bedspread on the wall, but there's not much else in there except his computer and (weather permitting) a jacket.