A substantial but semi-sheer or loose weave linen rod pocket drape in off white. One option Moos Belgian Heavy Faux Linen Solid Room Darkening Rod Pocket Single Curtain Panel
https://www.wayfair.com/decor-pillows/pdp/eider-ivory-moos-belgian-heavy-faux-linen-solid-room-darkening-rod-pocket-single-curtain-panel-w004536177.html

Hi - beautiful room and love the rug and bed! I can't necessarily recommend a particular fabric for the curtains but I can tell you that I did a window treatment that extended almost two feet on each side of the window and full to floor (not dragged on floor), hung closer to the ceiling. It gave the room an incredibly sophisticated look. My wall looks like it's all window! I put shears under it and leave the shears closed during the day but pull the curtains back on each side. Also, I would recommended a white or ivory bedspread and fold your quilt at the foot of the bed. This way, the headboard isn't "fighting" with the coral colored quilt. One more thing - I have a black curtain rod so the room has "a touch of black," which is nice.

Lovely space! The furniture are beautiful!

Here are some ideas for your reference.

1. Try to choose linen texture or sheer white or cream white curtains. It is good to brighten up the space and increase breathability at the same time.

2. As it's a bedroom, if you are more concerned about privacy and sleep quality, try to choose curtains with good blackout effect.

I hope this will help you in the window treatment!