Drapes. Hang the rod a few inches from the ceiling and the drapes should just kiss the floor. They should be twice as wide as the window so you'll need two 100" wide panels. Make sure to hang them a few inches beyond the window frame so light won't filter in the sides. You will want light control so be sure they're lined.

Tia, Hunter Douglas makes a designer screen shade that comes in many colors and will easily install inside the window. If you want a stronger look a bamboo (type) shade can add texture and would play off your headboard nicely. I would mount the "bamboo shades high close to the ceiling (after adding a 2-1/2" crown molding) and have 2 stationary panels to add softness and pattern on the sides off the window as far as possible. Let me know if you have any more questions and have fun with your project!

Mark