What about adding four similiar mirrors in a pattern. Hang them close together, almost touching. You could replace the light with a long cylindrical pendant.

I had a very similar space- 2 story and had a painting done for over fp. It's a Carribbean market scene with stunning colors and a wow focal point that enhances the room

The ideas above are really great! I am loving them.
In high end homes, where a high ceiling is typical in the formal spaces, we often build the fireplace surround way up for a dramatic and luxurious look. That is a costly proposition (much more so than the great suggestions made above) and will depend on the look and feel that you are after (see attached images for a couple of example). Good luck!

Perhaps, something like this might work, if these are the colors you are looking for.
http://ben-and-raisa-gertsberg.artistwebsites.com/products/tapestry-ben-and-raisa-gertsberg-art-print.html

Or, if colorful abstract art is your thing, please check out our galleries here on houzz to see more. Enjoy!... Raisa

Enjoy the open space. :)

you can use decorative tapestry above to this fireplace.
Here you can see exotic collection of Indian sarii tapestry
http://www.mogulinterior.com/beaded-tapestries.html

Hire a local artist to do a simple painted design. You'll love it.

I like Kathleen Jennison's idea - replace the light above the area with a long pendant or chandelier style fitting. The Houzz chandelier section under Lighting has quite a few cluster styles. Then a long bevel edged mirror on the wall behind it would be great.

I would go with a tapestry above the fireplace.

Love Kathleen and Megan's ideas. This mirror could be wonderful if it is framed in the space properly. From Uttermost http://www.uttermost.com/p-2610-amiel-large-arch.aspx?EID=7&EN=Category 42" wide x 82" high

https://www.houzz.com/photos/2011-hhl-living-room-contemporary-living-room-phvw-vp~135997
a piece of art https://www.houzz.com/photos/wills-creek-contemporary-living-room-vancouver-phvw-vp~40438

Have you thought about a mural? If not maybe paint a few shades darker than the wall and add your artwork. Glass tiles in muted tones to match the existing wall color. Something to make it stand out because it is a really beautiful feature.

If you added the chandelier that was mentioned above it would really make glass tiles sparkle. Love the chandelier or hanging light fixture idea.