Both a mirror or art piece can work above the fireplace in a moody green room, but the choice depends on scale and style. Use a tall mirror to reflect natural light and visually enlarge the space, or a large vertical art piece to add color contrast and personality. Make sure whichever you pick is proportionate to the wall for balance. This enhances the fireplace’s role as a focal point and complements the room’s moody vibe beautifully.