I'm not a big fan of mirrors that reflect ceilings. However, if it would fit with your decor, you could age the mirrored surface so that you could get the sparkle without a specific reflection.

I would consider refacing that fireplace with something to go to the ceiling as for the mirror always think about waht is reflected when you hang a mirror , most of the time nothing worth seeing twice so look for art a much nicer choice and hang the mirror in an entry or somewhere else.

IMO mirrors need to reflect something worth seeing twice so what will it reflect . Id a gree a pice of art would be a much nicer choice if you insist on a mirror it needs to be wider than it is tall so the French country one does not fit that discription at all. The layered look could be interesting but again reflections are everything

Take the decor items off the mantle. They are too small to be effective. Switch the square art near the window, with the mirror. The square art is squished in that space and will look, I think, great over the fireplace. The mirror near the window will reflect both the view outside, and reflect light into the room. Remove the long rectangular art to the left of the book shelf. Too many contrasting rectangles everywhere in this room, including the blinds. You need to break that up. I see 2 round pieces of wall art, one on the wall near the dining table, and one on the floor. Can we see them in better close up? It's possible that the round one would be even better than the square art, over the fireplace. Is the fireplace wood or?