Sometimes the simplest idea is the best. These three or four squares of color, appliqued at the inside corner of a pair of curtains or at each corner of a single panel might be just enough accent for your room.
Three Square/Four Square, #115/#118, 3 inches x 3 inches
This corner motif was inspired by a stained glass window. The original window was in blues and greens with golden brown stitching and applique at the base of the flower, but the design is also lovely in purples or in soft rust and persimmon.
Madison Iris, #203, 6 1/2" wide and height,
approximately 1/3 curtain length or 26 " maximum