As seen in this photo, a good idea is to dress the hearth with a fireplace surround. Your local Lowes should have the mantel and trim which you can paint or stain to the color of your choice. You can choose any tile, stone or beadboard to dress the inside of your fireplace facade ( like they did in this picture where they chose a marbled cream tile. With a wall that large, just make sure you choose a good scale and don't go too small or too large. It should be a focal point without overpowering the entire space.