Simple Fireplace Mantle

My living room has an old coal fireplace that's been closed up, so now it's just a part of the wall that jutts out for no reason. Someday I'd like to open the fireplace back up, hopefully making it usable, and add a mantle. Our TV is already mounted on this wall, so it would have to move up a bit. I've been looking around at mantles (not that this is a priority project or anything) and they've all looked too bulky for the space. This would be a simple solution -- and I bet pretty inexpensive, too.