We ended up with some mirrors mounted a little too high and just decided to leave them because re-mounting would have been too damaging to our surface (wallpaper holes would have been visible). We're getting used to it in time and are filling the area below with more decor. If you're going to put a lot of mantle decor there after the holidays as well, the mirror honestly doesn't need to come down too much. You might be able to just lengthen the hanging wire to get it down a little, if that is how it is mounted. The decor you have is beautiful!

I'd lower it a few inches so that it close to equidistant from the ceiling and bricks. Even if you add more bulky decor on the mantel, it can go in front of a mirror.

Is your light fixture actually as fabulous as it appears to be in the mirror?

thanks for the tips! And @Fori the fixture came with the house. I may switch it out because I'm not loving. Many others do love it however. I wish I knew more about it.

Hmm. Looks like an extra-fancy art deco slip shade chandelier (or a good repro). Learn to love! It plays nicely with the modern mirror.