If you are going to insulate, you would want to insulate the wall side more so than the room side. Doing this will hold the heat in your home as opposed to helping force heat out through the walls. I have seen different decorative designs for just covering the radiators, and they usually wind up looking like end tables. They have an open bottom, a solid, shelf like top and vertical holes right under the shelf for about 8 inches.
A simple google image search returns lots of pictures of how others have done so quite nicely. I don't know how well they work, but there is at least one way to find out...