A client bought some reclaimed wood at www.mrtimbers.com to install on the wall behind his toilet. It looks really nice. The wall was painted black first so you wont see through the knot holes or gaps. I leveled it out. I glued most of it and nailed a few full length boards to prevent sagging while it dries.

They also have paneling and fireplace mantels. Their website is nice with lots of examples in photos.