A friend who made a similar blue-and-ivory log cabin quilt had blue-thread feathers in the ivory furrows and variegated ivory thread feathers in the blue furrows. I liked it quite a bit!
Beautiful quilt! I'm a novice quilter, so I defer to the experienced quilters to advise you on how to quilt it. I just tell my LAQer to use her own judgement. She knows more about it than I do.
How about feathers in the white and a leaf design in the blue...check out some of the quilting designers for ideas! I would stick to one color thread...probably a light color.
KJEames