Give the feature wall one hard decision, and let everything else relax. This is the piece that sets the tone, so the sofa, the rug and the cushions can stay plain. The black background does a lot of work: it pulls the blue, red and orange forward and makes a quiet room feel deliberate rather than empty. Hang it in a living room above a low sideboard, on a study wall behind a desk, or at the turn of a hallway where you want a jolt of colour. Pair it with dark wood, tan leather, chrome and one flat-coloured ceramic. Skip busy patterned wallpaper and other loud colour pieces beside it. On fine-art paper the flat colour blocks stay crisp and the edges read sharp.