Is this fireplace in a den? Surround it with wood paneling. Put a wood mantel over the top and raised paneling above that. Is there a swordfish or a great piece of art from Africa? Hang it over the mantel. Place bookshelves on either side of the fireplace and panel the entire room. This will be a great retreat.
Will the fireplace go in a formal room decorated in a classical, perhaps traditional style? Encircle the opening with well-carved wood in whatever style the room will be: French Provincial, Queen Anne, Tudor.
Plaster the walls around and above the wood frame and place a gilded mirror over the mantel. The mirror should be large and impressive, with a frame just as ornate as the wood around the fireplace.
What if the room is more contemporary? Sheets of mirror above and around the fireplace frame will enhance the look. This frame should be flush with the mirror for a sleek appearance.