Can you layer a thin piece of white batting behind the center block? It would make the center more puffy. Just a thought.
I've only used black batting once and it was on a quilt that was primarily dark red and black. I quilted it with black thread.
I would think with that white background and that black backing you would have to be careful with your thread color. Tension would have to be perfect to keep white from showing up on the back and black from showing on top.