I think it works with the other decor. I have a suggestion for the collage: the large brown map piece is blending right into the wall. If you framed it in something black, the whole collage would feel more cohesive, as all the picture pieces would have a common black thread. Right now, the map feels like it doesn't belong.

a piano light or a short vase or bouquet of flowers. nothing else.

the piano is the star of the room and always should be

when i had a piano i never let anything compete with it. its art on its own. dont you think?

The map piece is a good size above the piano.

The collage elements seem too small for the space. Put the large piece in the stairway, then arrange the smaller pieces (minus the arrows) above the piano.

I agree with jbtanyderi, though I won't fight you on using the arrows (which I don't especially like, but then it's not my house). In any case, your gallery is undersized. As to putting something above the piano, I think that's fine. But try to find something that has meaning for you instead of using mass-produced stuff from Home Goods or wherever. I think an old painting that used to hang in Grandma's house, or perhaps a framed photograph of a favorite vacation spot, would make for a happy room. A cheap store-bought piece of art is not impossible, either, but only if you've genuinely fallen in love with some aspect of it.

I know that most pros hate seeing family photos in the public rooms of the home, but so what? If you were to frame up a bunch of small black-and -white photos of your grandparents, aunts, uncles, dogs, cats, etc., and arrange them gallery-style above the piano, I think your family would love it. It would be cheap, too.

Here is what we did in a design of ours, perhaps it will aid you in your dilemma.

I agree, nothing over the piano. Also paint the white vent same color as wall.

Agree paint the vent same color as wall.

When it comes to art just do what makes you feel good! Beauty truly is in the eye of the beholder. However I would paint the cold air return to match the wall.

5-5-75 will help you answer your own question. Hang things centered 5' above the floor, or 5" above furniture; keep hanging items within 75% of furniture's width. I agree, go big or go home with art in the stairwell. Triple the impact of the collage, and keep it big in size and scale.

I actually thought the art would look better where the collage is. No advice for over piano. I have three guitars hanging over mine. O.o