The most common mantle typically features a single focal piece centered on the mantle. The wall art or mirror should be at least 2/3 the size of the mantle. You can frame the single piece with sconces or other design elements.
Make sure to create visual movement by placing accessories of varying heights on the mantle.
Create visual weight by layering objects of varied shapes and heights. This can include layering artwork, adding small objects, and organic materials.