I dislike the vertical blinds a lot. Get some solasr shades motorized for that window and for the patio door. As for the FP why not a really dark blue for the wall then add that art .

If your vertical blinds are in good shape and you like them (I think on those upper windows is one of the rare good uses of them --- real MCM success!) then keep them.

Now:

Rather than put up that piece of art, paint the biggest part of the chimney that is the golden the darkest shade of blue in the art work, Then paint inside the niche the lightest shade of blue in the art work. (Don't paint the wall. Just the niche.that is part of the chimney.) Or do it vice versa: big field of light blue and tiny niche of dark blue.

I would hope you like it so much you can just leave it at that, but maybe you would like to put a white spiral of material in the niche. Or a very tall white ceramic, or a plant You could hang your art work between the sofa and fireplace -- or maybe after you paint the fireplace two different shades of blue, the art work would look very interesting hung on it -- but maybe hung on the upper right half, not the lower right half. Or think about hanging it over the entry to the kitchen, but off-center, well to the left.

The point is to work with the architectural big blocks of your constructed space. They are all off-center and juxtaposed, so try to create your own juxtapositions with color blocking.

(I was looking at this below other day. It might look really interesting in your niche, painted or unpainted)

https://www.chairish.com/product/6625304/tall-rustic-mid-century-wooden-spiral-hand-crafted-hanging-vintage-home-decor

The fireplace brick needs a different color. Whatever that is is not working.

I actually like "the wave" there very much. What was it about the piece that you felt didn't work there?

It feels like an abundance of rectangles when looking at the whole, plus the wave painting doesn’t seem to have enough of the other colors in it, like gold and beige.

I see what you mean about a lot of rectangles, but I also think that's ok. Yours is a very linear space and it has a cool vibe about it. As for the art not having certain colors in it, it's my opinion that artwork should be chosen because you love it -- not because it matches the rest of the space. Matching artwork to the furnishings or other elements tends to create a flat and uninspired look, whereas living with art that truly makes your heart sing personalizes a space and gives it life.