As I've posted previously, our three boys have their own room at the office, an upstairs nook behind my office where they can play games on the computer and work on homework, with each having his own study carrel-type space and hatch (note the black square in the wall) overlooking my office. They finally got to try it out last week, and really enjoyed it.
They haven't decorated yet (at the old office they had all sorts of school drawings and things posted) but we'll get those up soon enough, I'm sure.