Try painting the wall with the fireplace a richer, darker color. Place an eye-catching piece of art above the fireplace. The eye will be drawn to the rich paint color, fireplace and art. Place the tv on a dark stand near the fireplace. It will blend in with the darker wall and you will be able to better hide it in plain site. If the living room is really long, you can consider painting the opposite "short" wall the same rich color and making that into another seating area with a purpose like library/reading area/game area. The rich paint on both walls will make the room seem less rectangular.