The solid dividers are generally cheaper to buy. As for cool tack rooms ideas - I think a sink would be nice, shelves, loads of storage ( you can never have too much, especially if your a tack hoarder lol). Keep a fully stocked first aid cabinet, and I think it would be useful to have extra buckles, latches, etc. A washer & dryer would also be helpful, but really that's just for convenience. Have an area for tack cleaning supplies, and, as always, loads of hooks, and a few saddle stands might be nice =) If your in the mood to decorate, maybe add a few horse posters, a hang-up book on braiding, anatomy posters, etc. As far as aluminum, I can't be of help, but i'm sure someone will answer your question sooner of later =) best of luck to your barn building!