I painted my living room three times in two years. Each time, the result was fine. Clean, even, perfectly acceptable. And each time, about four months in, I’d look at the walls and think: this is just a colour. That flat, same-everywhere feeling never quite went away. Then a friend installed a floor-to-ceiling forest scene in her dining room, and I finally understood what wallpaper murals actually do that paint can’t. They give a wall depth. Not in a decorating-magazine, abstract sense. I mean you walk into the room and your eye goes somewhere. There’s a foreground and a background. It changes how the space feels without moving a single…