I do think you have too much that matches. For art, I'd get what you love and not worry about whether it's the same size or "coordinates" or anything else. You might do a small gallery wall on one side (including one or two 3-dimensional pieces), and a large image (canvas or framed) on the other. But whatever you decide, don't go out and look for "art." Look for what you love; maybe you already have it!

I'd replace at least one of the lamps with something different since the nightstands appear to be the same. (Again, something you love.) If it's you and your partner you can each decorate or keep on your nightstand what works for you be it a plant, pictures, water pitcher, books, reading glasses, etc. These should be your individual islands that work for you and less a "decorating surface."

If the colors work for you, great! But I find them dull and uninteresting. (That said, I despise browns and beiges and grays so take my advice for what it is worth.) What colors turn you on? Use some of them in wallpaper, paint, curtains, pillows, comforter.

I did tall mirrors behind my lamps in my bedroom.

Stack two pieces of wall decor on either side of bed. Easier than trying to find long skinny items.

i'd do the mirrors just to bounce around some light.

hang art on another wall.

you have any throws w/a bit of color you can use for the bed?

or what about something at the foot of the bed like a bench or ottoman?