I wouldn't paint the mantle, just get a dark frame for the mirror or paint it yourself. Just a suggestion

The mantle looks fine. It is the mirror that doesnt look good there. The mirror doesnt seem to go with anything in your room. A round mirror with a darker color frame, would look much better, if you must have a mirror there.

I would like to keep the mirror if I can make it work there. It's from our wedding but I wouldn't be opposed to painting it...

I would find another place for the mirror where it reflects something more attractive.

I suggest you make the mantel longer for a more balanced look and paint it charcoal or black, the decorate it with more items such as shown below. 2 large black lanterns between the hearth and wall would also balance the the fireplace wall since the hearth isn't very long. I also suggest you paint the fireplace doors in black (can be spray painted with a heat resistant paint such as for barbecues).

How about putting the mirror above the shelving opposite the fireplace - it will then reflect the fireplace.

It’s nice that you want to make it work but that is not the best spot for it. It looks like the finish is quite similar to your storage cubbies, so I might try it there. Hard to tell size/scale Might work there if hung horizontally or as part of a grouping. Hang some art above the fireplace and then the mirror will reflect the art and the fireplace. eta: @terezosa / terriks, your suggestion wasn't showing when I wrote mine...great minds and all that.

Black paint may be your answer. Notice how the "window" is leaning on another, wider black framed mirror.

I like the idea of painting the fireplace doors black, should I paint the mantel black to match?

I would. If it is a wood burning fireplace make sure you get the correct paint for heat. My daughter used a spray grill paint. But, ask at the store for a recommendation. Mantle can be regular house paint. It's easy to do. Just tape off the glass before you spray it.

I wouldnt paint that cover black, its going to stand out more against the white painted hearth, looking at the room on a whole, it seems like a catch all area, I would move the coat rack to the wall the cubby is on to bring some balance to that wall, consider maybe painting the room a warmer tone. eliminate the cubby. and do very simple decor on the mantel. People can really only enjoy the fireplace here as they walk into the room do to the shape of the room there is not much you can do about that. Perhaps the problem isnt the fireplace, but making the room itself more cozy?.