Unlined curtains that use Ripplefold pleats and their special rods and tracks would probably fit. You can choose the fullness of Ripplefold pleats. Standard pinch pleats would be crowded.

Drapery · More Info

Long curtains would look great in here. Move your art from between the walls to elsewhere in the room. Do you actually need that desk in the room? How often do you use it? If you have to keep it there, place the curtains behind it and pull the desk out from the wall a few inches.

I’d think about full single panels for each window that can be pulled open & stacked back to one side of windows. The 2 on same wall would stack back to each corner & the single window would also stack back to the left of the window. When closed, all look the same, when open the stacking back is uniform & not in the way of furniture or art.

You have a classic room with nice architectural features, and curtain panels would look great on your windows. I'd treat each window separately, with two panels on each window.

Nantucket, Ma. · More Info

Your window trim is so substantial and bold, it will be easy to overwhelm draperies. I would be sure to not go too skimpy on draperies. In the corner, I would have the draperies meet like this to fill the space (not this color or style, just showing for hanging example) and then be sure to have the curtains on other side of the solo window (or you could skip a curtain on the right of the solo window) and between the two windows and on the left of the left hand window pair be full and heavy enough to complement a corner like this.

Please post an update when you are ready.