Here is a creative idea, and perfect if you have multiple windows lined up and you want the repetition. Or if you have limited yardage of your fabric.
This treatment could be a "no-sew" treatment if you are handy with iron on adhesives and a glue gun. The striped layer underneath looks like it curves up a little at the bottom. The "swag" part was actually flat so you would just create a pattern for that. Surely the fringe was glued on! The whole thing could be stapled to a small board for installation or even mounted on a tension rod if you are able to install it inside the window frame.