Do you want the view? If not how about some kind of stained glass. Or you could tint it. What are you going to do with the wall? Wallpaper again?

Angel, I need a kind of curtain, blind for the window, and for the wall, yess wallpaper again...

Just a great window film and no wallpaper. Let the window become a piece of art.
https://www.houzz.com/photos/64-coachwood-road-contemporary-hall-calgary-phvw-vp~1767596

I do like that idea on the right, make it look like a piece of art on the wall. Do a very neutral wallpaper.
Maybe put some wider trim around the window and make it look a little bigger. Or a roman blind to co-ordinate with the wallpaper you choose.

iplay, what is the material of the second picture?

dear angel, what kind of wider trim?

My first thought was a window decal too, it could look so beautiful. Otherwise, you should choose your wallpaper first, and then pick a simple, easy-to-use plain blind in a colour that blends with the wallpaper. Let the paper be the star of the show.

If you're not fixed on using patterned wallpaper and blind or drape, then I think nothing could look better than iplay's second picture. That would be my choice, even if it makes the stairwell a bit darker.

Yes Rina, I hope I would fine a nice wallpaper to this wall, but is your opinion, stripe or floral or others? my surrounding wall is in brown tones, please advice me the color for this stairwall..and then I would go to find the plain blind.....

The surrounding wall could be a very soft, very light beige. You could also go crazy with a really strong, deep colour -- peacock blue? -- but I suspect that's not your style. A light smoky blue would be lovely.

For the wallpaper, I'm assuming a light beige or creamy wall on my picks below. Not stripes -- vertical would make the space seem unnecessarily high and horizontal would look as though you're trying desperately to cut it down. Big pattern, and you can go quite dramatic. The metallic shine in the top two posted below would add some light reflection to the space (not a lot, though, unless there are windows opposite the stairs with light filtering up and down). I think you could get a silverish or light gold in a blind to match -- not too shiny -- but you should check first if you like this idea. I love the bottom left one for this wall, it manages to be dramatic and subtle and the same time. Dead easy to match the blind to the background colour. The actual flowers in the fourth one are probably too small for such a big space, though I think there's quite a big, spacious 'repeat' in the pattern, but I have the feeling it could bring a lightness and brightness to the space with its femininity. Again, no problem matching a shade with a pattern like this, whether you want to use the background or one of the colours.

The other possibility, which could look really good, would be a diamond pattern -- but not black, like the one below. It was all I could find with the right pattern, but in your space it would make you feel as though you're living in a coal mine.

All these are from www.grahambrown.com

With blue or cream walls ...

Must go shopping now. I'll check in later.

Nice window! don´t make it so confused with busy wall covering. just put some neutral color wallcovering. and then, if you can, install a Kind of chandelier with Long drop.

I agree with Angel18432 beef up the trim around the window something around 3 1/2 inches wide. I think it would give the window a bit more weight and appear larger.

It is a solar shade, Marlins…
http://www.deliashades.com/

Stained glass or window stick-on that mimics stained glass look!!

here's a nice example of a simple geometrical peice

kcar : thats looks great...I dont need anything else around window, just it. the above picture similar with the glass at church's window, isn't it ?

There are some stained glass kits out there that use liquid lead & paints & aren't very hard to do (this is a cost saving way) or go to a stained glass shop & they can make to order---maybe hanging ones that you could switch out for the seasons & or your mood!!

Go with a Hunter Douglas roller shade.

Yes Marlins, that is the kind of thing they have in church window.

HI -- This window could be a great feature for the house . I would use panels of an Indian fret -work folding decorative wood screen, framed if needed to fit the window . If the panels are wider I would just install over top . You can also get laser cut metal or wood panels also. Or get a semi -sheer printed fabric or a lace ,- stretched over a frame to cover the window , this would be the cheapest to do ,I think . There are also window vinyl's that can have an image /pattern printed on and applied to the glass . There is also plantation shutters - but that would block a lot of light . Not so sure about the wall paper , that would depend on what you do with the window covering I guess . I would just paint .