Those are very beautiful! I have painted on fabric for quilts in the past although yours are so much nicer than mine were! LOL. I sometimes trace a design in the fabric and enlarge it, then reproduce it for a center square. The last one I did as an applique. I haven't painted in awhile.
I think a nice multi-colored floral fabric would look really pretty with your blocks.
Please be sure to post again when you finish it! :)