Wall cubes and glass vases filled with sand hold an array of seaside artifacts. Any grouping of related objects displayed on varied-height risers (or stacked books) can become a stunning fireplace focal point.
All-white vases in different sizes and shapes offer a visually united vignette for displaying fresh flowers. Or use a big vase with lush silk hydrangeas or a large potted Boston fern to decorate the space.
Vintage baskets fill empty space while offering the benefit of seasonal storage. Also try stacking trunks, interesting old suitcases, hatboxes or small footstools.
Leaned against the back of the fireplace box, a mirror doubles the impact of a simple arrangement of ceramic garden spheres and one twisted branch. An artistic sculpture or a unique architectural salvage piece would also work.