Man, I wish I could get my bows bending that much. Even with backing and 1-1/2" wide limbs, I'm getting excess set or breakage when I draw more than 22" on a 48" bow. Great job!
Most of the plains bows I've seen don't have much paint, if any. If painted, the backs are usually a solid color and the bellies painted with simple line designs. Coup or kill marks (usually circles) might be painted on the back. Sometimes the sinew wrapping or the handle was painted. Rarely, you will see etched or burned designs. Many bows were simply stained yellow, red, black, or brown. Snakeskin backing was very rare...and was probably never used in the Southern Plains area.
Horse hair or human hair tassels were fairly common as decoration. Sometimes you'll see a feather as well. These were attached to the top of the bow.
Quill work and streamers of fur were sometimes put on bows belonging to important individuals. These were attached mid-limb on both limbs. Beadwork was seldom added to working bows...being reserved for ceremonial or tourist bows.