You're right that you have two much repetition of the same shape. I would place two on each side of the fireplace, one above the other, and get a vertical or horizontal painting for over the fireplace. When you rehang the pieces, leave just 2" between the pieces. The bottom ones should be about 42" above the floor.

Another option would be to move the two that are currently flanking the fireplace in a different part of the house, one above the other so that they do not exactly repeat the ones over the fireplace. Then you could leave the two over the fireplace but move them so that there's only 2" of space between them.

I agree, it is a bit "blocky". I think the decorative squares are a very nice touch though. To counter the blocky look, I'd put 2 squares stacked (with a small gap in between) on either side of the fireplace, but would counter the "blocky" look by putting a horizontal/rectangular (or horizontal-oval) mirror over the fireplace. A mirror would add more light, and would be a nice mix with the decorative squares on the side.

It is a bit square, but it might be interesting to squeeze all four of them in above the FP very close together. Then soften the vignette by hanging a pair of drapery panels on decorative rods close to the ceiling. Use just one panel on each window, pulling them back right and left for a draped effect with hold backs. If you don't want drapes, consider glass shelves and a display of large dramatic colored glass inside the window frames. I'm not a fan of skinny floating shelves, so would remove them from the TV wall. Take them to a hallway and use for leaning large framed family photos.

https://www.houzz.com/photos/2012-new-american-home-contemporary-staircase-orlando-phvw-vp~549845