How do I light the fireplace effectively as a design feature?
Put the TV in the nook, not above the fireplace. Keep the screen at seated eye level on a low console or within a built-in that brings the TV forward, and use the fireplace for art or a mirror. If glare from nearby windows is a concern, add a tilt/articulating mount and light-controlling window treatments. If you skip the TV, the nook is ideal for a dry bar, slim desk, or bookcase with closed storage below.