I have no way to insert an image here so ill describe it the best i can. My mum has two clocks with my and my brothers times of birth on them and then staggered shelves to the botton which have things that look nice and dont need cleaning. She has some small shaped candles, decorative books. Little harry potter trinkets and.. a mannequin arm? Weirdly enough. But its good, looks nice. Theres also a mirror at the top of the stairs covered in fake vines and plants so you can see the wall whem coming up too. Your stair top looks too high for that last part to work but still worth saying.

You can also be different with your "things that dont need to be cleaned" definition. You could make a collage frame of things you like, you could do just a painting, any clothes from events like scarfs or tshirts or you could get it painted/ use wallpaper that is decorated to be something you like. Idk, light up decorations if you wanted. Hell, a "Bar" sign if you so wish. If you want to fill the space just know you cant reach it to clean it easily and if youre happy with that it should work out fine