Another idea for the basement walls is earth plaster. You nail a bamboo screen to the walls as a base. Then you plaster it with 2 or 3 coats of cob. Cob is a plaster made from clay (like potter clay) fine sand and finely chopped straw,and a small amount of wheat paste and water. Instead of straw you can also use straw manure. This brings a real natural color to the walls. It doesn't smell once it dries. So we could actually have cow poop on the walls! It sounds pretty bad, but looks very awesome.