How tall is it? Post some pictures and you’ll get some good suggestions.

Sorry. This is my first time here. I figured out how to add the photos now. As for height, I'd guess both the mantel and the entertainment center are about five feet. Thanks.

Nothing. Empty space makes a design statement.

Do you think maps would look nice there?

My suggestion for your mantel would be to hang a large piece of artwork you love and nothing on the mantel. It's hard to recommend something on the entertainment center without knowing the style you like or what else is in the room. Maybe a large vase/vessel of some sort with tall leafy branches to fill some of the vertical space?
More suggestions might come in if you add more information, like pictures of the rest of the room and what your decorating style is.

What is the rest of your decor like?

Harold et William Harold and William Tapestry Wall Art Hanging, B - H 38 x W 27 · More Info

Novica Sunflower Farm Applique Wall Hanging · More Info

"Wick Fancy Hat Bands" Digital Paper Print by Vintage Sports, 50"x26" · More Info

Wild Apple Portfolio 'Geography of the Heavens III' Canvas Art, 47"x20" · More Info

Twinkle Twinkle Little Bat Framed Poster · More Info

Portrait Of A Woman Print · More Info

"Map of North America, 1641" Digital Paper Print by Joannes Janssonius, 18"x16" · More Info

"Corfu Lights and Shadows" Poster Print by John Singer Sargent · More Info

"The May Queen" Poster Print by Margaret Macdonald Mackintosh · More Info

My home is very traditional, camelback sofas, wingback chair, brass lamps, and an oriental rug to pull everything together. The color scheme is dark red, sage green, and a golden color if that helps.

Do you like fabric art like quilts, or maps. or other things related to history? Do you want something on the wall or prefer things sitting on the mantle or entertainment unit? Would you like real plants there?

I am looking for something to sit on TOP of the entertainment center and mantel, not on the wall. I don't do live plants.

I would shop at an antique store. You can get some great ideas and props there.

Without seeing the rest of the room, it’s hard to tell what would look best. Think larger rather than smaller, so big art and not small knickknacks. I’m a fan of modern art with traditional furniture for a more eclectic, less cookie cutter look but that’s just me. A landscape painting or large mirror over then mantle (depending on what it reflects) could work nicely as well. I also agree with the commenter above that a large vessel with branches would add some height to your decor. Please stay away from a gallery wall and word art.

Let’s see how many suggestions we can make that you can be angry about for being so wrong:

Do your guests drink wine?

Four Bottle Acrylic Wine Rack · More Info

Kohler K-8628 1-3/8" - Charcoal · More Info

Pemberly Row 3 Tier 12 Bottle Wine Rack in Light Oak · More Info

Nothing on the mantel - switch out the dated wall piece that you currently have above the fireplace for a large, colorful piece of art; for the entertainment center, do something like this on one side and then leave the rest of the top empty

^ Exactly what I was going to say!