Paint and wallpaper aren't the only ways to put gray on your walls. Here, a lime plaster stain was used on the walls, which gives them a nice texture and depth. I love the floating, cloud-like feel of it. Your paint shop should sell coatings in a range of colors, from a misty light gray to a dark charcoal. There is also ready-made paint which claims to mimic this sort of treatment, but I've never seen it used.