I actually really like the look of the mirror. It's all too predictable to see a painting about the mantle. If this were my living room, I would surround it with other things. You could place a small clock in front of it or some art next to the fireplace, like you can see here. I can also see what other posts are saying about covering it, but I feel that would make the room feel much smaller. Mirrors help make rooms feel a little more open,

I love your windows and angles! but the curved arches and columns are fighting them badly. I love Beverly's mockup. If you did that, I'd recommend also squaring off the arch between the columns, and getting rid of the weird mirror niche that's to the right. (I suppose your house is full of arched entryways and niches? that could be a big job, but you could tackle one room at a time.)

@marys235 - yes, that’s exactly what I mean! If the Vase is that narrow, your “gallery” of various smaller size of arts could be extended down the full length of the niche. Place the vase & experiment with paper cutouts to help visualize the look. If you have small paintings or pieces you could place them too for a better visual. The vase color & style as well as your decor would determine what kinds of frames & art you hang there. I’d use 3M Command strips for hanging since the pieces would be lightweight & that would give you flexibility to move the pieces around without making a dartboard out of the wall! 🙂. At the very least, my suggestion is probably the easiest to implement and will help you decide if you like the result or instead want to have shelving or another permanent change to the niche construction. And hey, if sometime down the road you see a piece that you fall in love with & that fills the space - well, you have the option to buy it!

An idea... eliminate the middle piece in between the squares on the top and bottom. Add a large TV in the top and wide electric fireplace in the bottom. Maybe a beverage fridge can fit in that nook by the windows?