At Spade and Archer Design Agency, we define a case good as any non-upholstered piece of furniture such as a desk, buffet, dresser, or a credenza.
When selecting a piece or pieces of art, we use art that is at least 50% as visually large as the case good but no more than 100% as large as the case good. In this shot we can see the artwork is about 75% as large as the buffet. We center the artwork on the case good, and hang the artwork about 4” above the back of the sofa to the bottom of the artwork. Note, 4 inches about the size of your fist from the pinky to the thumb. We are never afraid to place a lamp or lamps in front of a piece of art and love the way it gives the room a depth of field.