When accessorizing the fireplace mantel keep the surrounding wall areas in mind. If the fireplace is surrounded by bookcases or open cabinets, the accessories perhaps should be more simplistic.
What is placed on and above the fireplace mantel can change the shape of a fireplace area, can enhance a ceiling height, can draw you in to see a painting close up. It is indeed a focal point and should be treated as one.
Fireplace mantels are a blank canvas and you are the artist. Create, step back, tweak, step back, take away, add, step back, got it! It's a dance between you and this space of your home. It will come together - just approach it with an open mind and a collection of things that make you smile.
Image Sources: Joy Tribout, Courtney Giles, Architectural Digest, Arcadian Home, Pinterest, House Beautiful, Picasa Web