I don't have any suggestions for other then wood, but, I do have one piece of advice to offer. We have three barns, one is an old wood barn that we built in the 80's it has wood stalls, our stallion barn that also has wood stalls. Then about six years ago we added an indoor. This indoor has a round pen, grooming area, feed area, I could go on, but I'll get to the point, everything is movable. When we set it up we knew we were getting on in years and wanted everything to be moved in case we needed to put in the tractors, mowers, store hay, whatever. So to get to the point, we bought 8 x 8 metal panels. It has worked out great since I can put in up to 10 stalls, or change them around, and make double stalls, house the show horses, etc. Well yesterday I found out with a colicing horse, you can't put a sick horse in one, they will get their legs caught in the slats, so I moved her to a wooden stall. Better to have a thrashing horse get cast them have them break a leg. I do have pitures, I'll see if I can post them but I have dial up and sometimes opening two windows at a time is not going to happen.