My parents house is heated by a hot water system that uses Slant Fin baseboard radiators that were installed in the 60's. Especially in the bathrooms, the covers are looking pretty bad due to rust, multiple layers of paint, and general wear. I was thinking that I could make a replacement cover from wood (oak) to match the rest of the trim in the bathroom. I'd remove and discard the front and the moveable louver (they leave them open all the time anyway.) The replacement would have a slot at the bottom to draw in cool air and one or two at the top of the face to let it back out, similar to the metal covers.
Safety-wise I know I am OK with this plan as all the copper plumbing is run through wood floors and attached to wood floor joists. I'm more concerned about affecting the heating of the room and the affects of the heat on the wood. People make radiator covers for the old fashioned cast iron radiators all the time, so I would think this would work too.
Replacement really isn't an option. The housings were attached to the exterior plaster over brick walls with concrete nails before the plumbing was installed, so there isn't any easy access to remove them. Stripping would be a lot of work I really don't have time to do, so the other option is just another layer of paint.