What you've got is timeless. Unless you want to make a big decorative statement with the fireplace that governs all your subsequent decorating choices, suggest you furnish and decorate first, then revisit the scene. Be aware that fireplaces have codes and safety requirements as to materials and distance from the flames, so no DIY without making sure you know what you are doing legally and safety-wise.

Be careful however you decorate the fireplace (or other parts of the room) it doesn't fight the many arches that are a permanent strong feature of the space.

Thank you @mytwo cents. It seems like the inlays on both sides of the fireplace were put there so they could be tiles or something. I actually like it all white/plaster would would rather not have the inlays at all…. but open to suggestions. Wonder if I should have the inlays filled? Good call on code, that is something I will have to take into consideration.

the room is quite mediterranean in basic structure (or perhaps southwest USA if that is where this house is). You could pick in advance a tile, but unless it is very low key it will determine all the rest of your choices for the room. Everytime you think about a new rug or a lamp or a sofa you will have to wonder whether it goes with the tile. Whereas if you wait until you've decided the feeling for this room -- earthy, beachy, grand villa, lively pop fun? -- you can do whatever with the fireplace that plays off that.

If you have some ideas what you would like might be worth your while to see if you can experiment with your ideas with peel and stick removable wallpaper. But you needn't be in any rush to decide. You can put a simple circle up there and it would look great.

Were it my space I would probably do modern Neapolitan tiles and float neapolitan angels up there -- but you probably have different ideas

This is a double sided fireplace, no? The flooring is different in your kitchen vs. your living room? What is your aesthetic? How do you plan on furnishing your rooms? I agree that something simple in the tone of the stucco/plaster would work with anything. The space is beautiful and the lines of the fireplace are elegant. Perhaps a handmade tile in the color of your walls, with grout of the same color?

Add a mantle and surround.

Love Marymut’s idea. Beautiful fireplace but as it’s black, that’s all that stands out. I’d add decor first and pull a color from that and add it to around the fireplace to pull the room together

I would look at Pratt & Larson Tile.

I used this P & L tile when I remodeled the fireplace in my previous Spanish style house.

Use fluted stone tile that matches the counter?

The black box needs to be hidden with a nice fireplace screen. Choose a finish that matches or compliments other hardware or fixtures in the room. Shown with and without a neutral marble slab surround.

Dark Bronze Wrought Iron Fireplace Curtain Screen (finish is similar to ceiling fan)

Dark Bronze Wrought Iron Fireplace Curtain Screen with Taj Mahal Marble

Antique Silver Fireplace Curtain Screen with Decorative Casting Trim

Antique Silver Fireplace Curtain Screen with Taj Mahal Marble.