There are a variety of companies out there selling radiator cabinets - metal and wood. They add a nice touch to a small room too, since you can put things on top of them. Not cheap, but at least it'd be enclosed and if it was wood then you could put those foam bumper guards on the corners to prevent any corner accidents. One company I like is http://www.woodenradiatorcabinet.com .
We, too, have radiators and are wondering what we'll do for the ones that we don't have covers for. The ones at that website Chicagomom posted are beautiful, but dang it that they aren't in our price range.