How about hanging some beautiful wall paper on the backs of each one of these openings

It would be a pretty big space to have absolutely nothing. Yes find some simple art in similar proportions to the openings. Or if you want to keep things very subtle, find a simple textural wall paper for inside the niches and maybe one black objet to put in the center. (small medations or flowers, long simple trees?...I didn't find anything that I thought was perfect at a quick glance online.) Have fun!

try art.com. maybe pick a series, a trio that flow together.

Oops make that 27” x 44”

Take it as an opportunity to display your treasures- souvenirs or collected items that reflect your personality and/or don't seem to fit in with your other rooms. Guitar collection aside, you must have or will find rarities that speak to you. Trade them out as you see fit

It's hard to tell from the photo if the re are flat or if they are also curved along with the wall. If your cutouts are flat, you could consider a wall mounted fountain. One that would specifically that would look really beautiful in that space would be the Whispering Creek Wall Fountain. This fountain is 46"H x 22"W x 5"D and does have to be mounted on a flat surface. It has a wide variety of frame color options as well as surface materials. Below are just a few images of the different options available.

Why in the world is Maureen Fereira above suggesting to put benches there? It's a staircase for cry eye!

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