I wouldn't change the mantel. It is currently simple, but it coordinates with the hearth. Instead, I would focus on the other things around it. First, clean the brick above the fireplace opening (and check your flue- it may need cleaning). I would look for sconces that are slightly larger and fit the style of your home and furnishings. It's hard to tell with just this one photo, but maybe a lantern style? The other option is to remove the sconces, and add a tall floor lamp in the corner instead. What other lighting do you have? I would look for more colorful artwork to use above the fireplace, and then leave your mantle bare. Remove all the too small items from the mantle and the plate below. Put your bowl on the end table instead of drawing attention to the floor speaker.

I like calidesign's suggestions.

Nice room. Does the hearth extend all the way to the right wall?

What are your specific objectives?

Mantel and Art:

Are you wanting more "warmth" for this wall? If so, have you tried "warmer" -- more colorful -- art?

Like that the mantel and hearth match and have clean simple lines so I wouldn't suggest you remove or seriously alter either. The art "goes well" with the simple gray lines of the mantel and hearth but the absence of color gives off a less than warm vibe.

Would keep the top of the mantel uncluttered: You might try different combinations of items on the mantel such as one tall item on one side and a grouping of smaller items on the other side. Probably would not put anything in the middle between them in front of any art you hang above the mantel.

If, however, you do want a change to your mantel/fireplace itself to add "warmth", you could add to what you have. For instance, if you're wanting to add wood back to that area of the room (after having painted over wood paneling), then, after you scrub the brick clean, you create a faux surround: you could wrap the corners of the brick -- fireplace and hearth -- with boards using the wood finish you want and then add a pair of boards in the same finish horizontally beneath both the mantel and hearth.

Sconces:

You might consider replacing the existing sconces with larger (more modern styled) ones that do not have you looking at or into a "candle" or directly at a light bulb or into a light -- something that provides light, both up and down, but doesn't glare at you. Also, experiment with different kinds and colors of bulbs until you find the vibe you want..

https://thekairoscollective.com/large-pair-of-wall-lights-sconces-french-midcentury-holophane-glass-flush-mount.html

Surrounding area:

Very much like the the colorful "plate" on the hearth. Also like the colorful lighted bowl on the right. Not a fan of the stuffed toy in it ... but ... it it is there for sentimental reasons, then keep it -- Your space needs to reflect Your interest. Have you tried adjusting adjusting the display of the bowl on the right to create more symmetry with regard to at least height as to what is at both the left and right of the fireplace.

Question for you: I have a "corkscrew" candle holder I bought for a dollar at a thrift store. Except for the center wood dowel, it's all curved metal -- just wider curves at the bottom. Not that I needed it but I found it interesting and thought if I ever actually used it with a lit candle that I might set it atop a small metal tray. A standard "emergency" candle, however, doesn't stand upright in it (leans) so I was wondering if the size of the rings is the issue or if you have a sharp nail or pin in the top of the wood dowel or use something else to hold a candle in place.

Do post a pic to let us know what changes you embrace.

Thanks for your ideas! The hearth does extend all of the way to the wall on the right. The reason for the interest in a mantle change is because we've never 'warmed up' to the stone mantle and have always liked the look of rustic wood mantles. We would like to keep the print over the mantle where it is because of sentimental value. We had it in another spot but missed seeing it all the time. We'll clean the mantle of the clutter that's on there now. (We put the candles in the middle because there is an outlet behind them that we like to cover up, but do utilize it around the holidays). The stuffed toy is only there temporarily as a light reminder from a recent hospital stay.

As far as the candle holder - a regular candle fits in ours. It's a variation of a 'Courting Candle' used from the 1600 - 1800's for a suitor to know when their time was up and they had to leave. The father would light the candle and the daughter and her suitor would visit in a sitting room until the candle burned down to the top of the first iron coil. :)