I really like the idea of vines and flowers for the border. Perhaps use just the colors in the vines and flowers that you already have in the quilt. That would complement all of the angular lines in the blocks and not add any more angular lines. I like your quilt and the colors you used. It is very nicely done. I would bind it in the darker blue if possible (meaning that you have enough of it.) I will look forward to seeing your final decision.