(I'm posting a ton of photos and ideas since you have a lot of potential for that fireplace design)

The marble really won't go out of style. it's a little safe though.

basically would look like this (but without the hearth)

do you like this? Do you have any plans on switching out that area rug and all the brown/tan? the marble is rather cool, and your other elements lean toward the warmer side. You could choose a Calacatta marble instead of that carrara.

Shown here in a subway tile format. see the warmer gold tone? I love this reclaimed beam mantel.

(I still think a new rug would benefit this area greatly!)

heres the sample you have showing the 1x4" herringbone. (my first pic is a 1x2 or 1x3 size)

diff ways to tile that and the hearth. I'd go even w/the hearth width and get one of those reclaimed beams

I'm kind of digging this look too. (and the very last picture) ignore the raised hearth.

you could do this in a glazed ceramic mini brick tile, or even your marble. but I would carry the wood mantel (thicker) from side to side. lover how it's styled too

you could try something like this, add a nice white hearth inset in the floor, and do a different rug and artwork. this mantel is a bit more modern looking. tile is a warm gray subway (2x10 is good)

I like the black a lot more. gives it some contrast and look nice w/your white and other tones.

it's a black marble (Nero Marquina in a chevron)

love this look, especially w/the black and white artwork, black/white rug

updated look,,,,, remove the more traditional white mantel surround, pick a tile (I did a 2x8 darker blue/gray in a herringbone layou) and top w/a thick wood beam mantel. bring in a nice tall potted snake plant, a basket w/wood, diff art.

black and white, updated mantel surround (see more on this below) and some vertical shiplap going up to your ceiling. style the hearth area, maybe some new art. (i'd get a new area rug too. you have a TON of brown going on in that room)

have you thought about bringing out the tile onto the floor for a hearth? you could weave it into the wood flooring for a nice effect

Or, get a solid piece of marble for the hearth. you can find remnants all over the place. this tile is an elongated hex in a soft blue/gray.

same shape in the marble with solid marble hearth, more modern mantel surround, and a vertical tongue and groove up to the ceiling

for a classic, timeless look, what if you got solid pieces of the marble or stone and did it like this?

you could update the entire surround by redoing the mantel to something like this. the stone surround could be a brush granite, or basalt, soapstone, slate,,,, this will always look good.

basalt is a good choice, or something like this honed black granite. look for scraps and remnants at stoneyards or fabricators shops.

On the portion above the mantel, (if keeping the white one you have) I'd like to see some board and batten trim work for a more finished look. not the best pic, but see how they did the trim piece all the way up to the ceiling? maybe some sconces on either side too. I really like the tile.

or, look at this vertical darker wood panels. if keeping your brown, this would look nice

I really like the Zellige tile. I'd redo the entire thing in this tile, swap out the traditional mantel for a nice wood beam mantel.

comes in all colors too. I love how this tile looks. shown in the 4x4. comes in a 2x6 and a hex too

another idea, (you could take it up to the ceiling.)

I love the solid black inset hearth, the tile, the gorgeous wood beam mantel AND the way it's styled. do the sconce overhead like this. you have the perfect corner fireplace for this design)

Corner fireplace decor ideas and layout for furniture

check out this one. lighter furniture (notice the dark floor) and look at the fireplace. this is a skim coat overlay.

this would look really nice w/your kitchen. has the warmer tones to work w/the grays/whites, a lot of texture, and the fireplace surround is more updated. new rug, round wood table, leather chair.

I'd really look into something like this. (and, even if you chose the marble tile, you could still do this look. )