Here is one option of covering the entire wall surface.

This must be the most asked questions. Those windows are so dated. It shocks me when I see a new home being built with them. I would hand drapery panels st the ceiling. Pull them back at a point that still covers the rounded window. You can leave some of it showing but leave the illusion of a normal straight window.

Dytecture that looks good. I was picturing a round top window. The arch looks great.

Dytecture, I really like that, too. It looks very elegant.

Thanks, hopefully it works for that home owner :)