What a beautiful quilt!
Forgive my lousy drawing, it's hard to draw with a mouse
. And keep in mind that I'm a LA quilter, not a hand quilter. But I would do a straight line down the middle of the black and white pieces. And a pattern in the red areas - I drew feathers since they're the easiest for me to draw (never would guess that from my drawing!! LOL). But you could put almost any design you like in there - a cable, leaves, whatever.
It's going to be gorgeous when you're done - be sure and post another photo!