I don't know anything about quilting Bargellos from experience, but I have seen a picture of one (maybe on this board) that was done with a stitch down the center of the squares following the curves from one side to the other. On yours, some of the lines wouldn't go all the way from side to side but from one end of a particular curve to the other end. I know it looked really nice and didn't distract the eye from the piecing. I think leaves or flowers might be distracting. Even though you couldn't normally make straight lines look straight, perhaps you could use a seam guide to stay pretty even down the center. I know you will get more expert advice that mine from much more experienced quilters.