The design in question is the background fill "behind" the feather motif.
With the fantastically decorated Biltmore in mind, I was drawn to some of my more ornate fabrics, and thought about dividing the long pointed pieces that form the cross of the center with seams to further replicate the Biltmore-inspired design of the blue and white wholecloth.
I hesitated to do that because the piecing of this block is already a challenge, even though it only has 16 pieces. The trouble is, every single seam is a dreaded "Y", and my idea of splitting the bars would not eliminate any of those. Then I realized I had this shaded fabric that would give the dimensional quality I wanted.
Many piecers deal with Y-seams by hand-piecing, but I have never liked sewing by hand. I just gave myself plenty of time for the cutting and marking of each seam intersection. I would probably not make a whole quilt of this block (even though I didn't mind quilting the design at all!) At this scale - four times larger than my quilted version, I will have to put some interesting quilting in those large shaded areas. Perhaps my Biltmore-quilting inspiration notebook will come in handy when I get to that point.