I don't think you know what you have. Bear with me - I've looked closely at your gorgeous room and think you are missing what this does for your space.

Go pin a lot of rooms with fireplaces and look at them for all the different details I reference here before you make some decisions - this is an amazingly gorgeous fireplace scaled well to the size of the room using REAL stone in proportion.

The bones of your room (ceiling angles, window profiles) are somewhat contemporary, and the stone now makes it work a with your transitional decor without your room being cold or stuffy, which is what your drywall / travertine mantle/surround option will shift it to. The lines of your furniture and the lines in your windows are not that traditional and the juxtaposition makes them pop where a travertine stone (mcmansion builders hearth) won't. Facing this with stone tiles in a contemporary pattern will work for the bones of the room, but will only make it less expensive looking and be more trendy/ out of date sooner. If you LOVED a really contemporary look, this would work - but I see your chandeliers and dining chairs and they are definitely more traditional / transitional. You can get some large horizontal stone tiles and have a stacked grid with grout lines if you decide to go that modern, but at this height, and scale, it will feel colder, since most of the stone tiles you would choose from don't have this warmth. I'm not sure you would love that either.

Real stone, like your fireplace, is rarely affordable/ used anymore. Some people buy it in veneer depths now, but never in the full depth you've got. It lasts forever, this one is at the perfect scale for the wall chimney, and has amazing neutral camels and grays that are impossible to find in the cultured fake stuff most builders use / they sell these days. Isn't this on the chimney outside your home too, so it has authenticity? I understand you looked and thought it was probably outdated, but this one really isn't - it is a classic stone profile and just gorgeous.

It is the warmth in your room! It counterpoints beautifully off the furnishings and art (wowsa - you have great things) that you have in the room. It isn't the stone that should bother you, but the insert in the chimney - you have a much taller/ more grand chimney opening that at its real scale will wow you.

Spend your money there, get that updated by a custom metalworker so you can enjoy the scale of the masonry opening that you really have - it looks like they cut it down to match a silly std door. Ask for a raw steel finish to echo your grays and later, if you still want more traditional elements, add a modern floating mantel made of wirebrushed timber finished and distressed in gray driftwood tones that complement the stone.

The scale of your stone chimney also offers the rare opportunity for a fabulous overscale modern art canvas on the upper chimney (especially without a mantle) to echo the contemporary chic you have going. Try that before you spring for a mantle - something gorgeous that you LOVE - and you'll see this backdrop differently I think as it will provide the frame for it. Maybe change the drapery to platinum banded trimmed camel velvet on grommets to layer the textural story you've begun with the shimmering chaise and celebrate the warmth of the floor and stone.

For the $ it would take to change the masonry, you can have a huge piece of new art, new draperies and a wonderful custom metalwork / glass hearth look. Those will do more for your room than any other changes, and may be bothering you more anyway.