I usually also do curved quilting on linear piecing and would usually go with feathers in the white squares, but somehow, I looked at your beautiful quilt and thought "square spiral" - easier on a domestic then on a longarm, but if you are using a longarm, just use a ruler to keep you straight. I would start about 1/2" into the block and go around, leaving an inch between the lines as you spiral in and then spiral out again between your lines - you end up with quilting about 1/2" apart, and an easy way to go into and out of each block without stopping and starting at each block.
Leah Day did something like this, except hers is much smaller, but it will give you the idea:
http://freemotionquilting.blogspot.c...re-spiral.html
I would make one spiral per block.