I also think the scarf needs to go. What is on the other side of the window besides bright light? Do you need to cover the window because of privacy or because it is so bright out there?? I do not like window covers, but in this case I would put something white in the windows...blinds or shades. But not like the drop thing you have already. I like that the top is left open. Do that again.

My suggestion would be the Home Decorating Forum as this is more about the nuts & bolts of windows than finishes.

Wow, just wow -- never seen any quite like that. A pic from inside might help. First thought: Locally at least , Home Depot and Advance Auto Parts (and likely other places), carry a plastic tint film that will help block light and give you some privacy during daytime; however, with the lights on at night, you'll need an indoor window treatment. Edited: Forget the corner cabinet idea; unaware the windows were in a stairwell. Louvered doors (installed as if the windows were a corner cabinet) painted the same white as the trim might still be an idea worth considering.

Yes a roman shade, inside mount. Easy Peasy.