Do you collect botanical prints? Display them on the mantel. It's fine to prop art up against a wall. Fresh potted plants act as perfect bookends.
Repeat rounds. A circular shape is a nice complement to the squareness of a mantel. Here they're used effectively in pairs.
A minimalist statement can also work on the mantel. Try grouping a cluster of like-colored pottery to one side. The visual weight of the grouping to one side helps create a modern vibe. A great-looking pendant balances the vignette.
A mantel can be your area for a rotating design element. If you like a little something fresh every week, use this spot to display fresh flowers. Notice how the designer used lighting to create a focal point here.
Why let your favorite china collect dust in the pantry? Consider putting a favorite dish collection up on the mantel for everyone to enjoy. Dishes can be mismatched or matching. Display them using small plate stands or easels.
Use location-specific accessories to make a statement about your home. I can visualize this rustic-looking door in the mountains somewhere.
Tell a story about your hobbies or occupation. I think this artwork is a classy way to showcase a riding hobby, a horse-breeding occupation or perhaps just a love of horses.
Let lighting do the talking. Perhaps the only change needed to your mantel is the way in which it's lit. Make a statement with interesting pendants or sconces in pairs or other repetitions.
Consider fresh paint. I just love the boldness of this high-gloss green. The color is unexpected and fun. There's no need to overaccessorize a mantel with bold color.