You really aren't far off. Lose the 'mantle'? shelf thing above the fireplace. No to a hearth the look is flat and sleek--as yours is. Paint over the gold tone louvers on the fireplace, or get a new door. Are those both doors that flank the fireplace? The missing trim on the bottom right makes it look like a door but I don't see a door knob.

This Since it's asymmetrical, don't call attention to it by putting something in the middle. Remove those lower two plants and candles. you could do a basket w/a throw if you like. I'd bring in a natural wood mantle (I used a thin one in the pic above) I actually like doing something above your fireplace so that it's more of a focal point. I'd like to paint it a darker color. black, a dark bronze, something. Maybe one of these darker colors Then I'd bring in furniture that looks something like this: I'd also do a hide rug, maybe layer it over a jute or sisal. if you like the lighter neutral tones: you could also do the wood mantle and do a bunch of plants. (no candles) another photoshop. I opened up the firebox and got rid of the gold. if you must keep it, consider painting it a matte black. easy to do what's on the sides of the fireplace? do you have room to do any built-ins or something? BTW, just for grins, if you want to see what you stone looks like painted:

A hearth may be required (depends on local code and type of insert), but a full wall of stone is not, so they should be able to do something simpler with the space -- however, if they do, they will probably need new flooring in the room, so that's something to take into account. I wouldn't aim for the TV over the fireplace, but a smaller surround will probably mean that the TV can move closer, making it easier to arrange furniture to enjoy both. And have art hanging over the firebox too! Honestly, once the stone comes down, the world is your oyster, so you just need to look at some photos and get a sense of what appeals and fits with the character of the house and your parents' stylistic preferences.

IMO the TV is too high above the mantel . I agree the 2 boxes below the mantel make no sesnse since it appears this is a gas FP. IMO get a linear FP if that is the only place for the TV and then hang the TV at a much better viewing height That eliminatesthe 2 boxes and puts the TV in the right spot BTW the surround you show and the tile do not work together. It is also always good to see your style so post that in a comment here do not strat another post.