Will this be a surprise for your granddaughter, or has she seen it? If she likes being part of the process, you might ask her to pick a favorite border. Of the 4 pictured, I agree with the choice of stripes run horizontally like waves. But I'm wondering if you have a soft lilac batik? I'm thinking the Dolphins would get more attention if you framed them in an analogous color.since your grAnd likes purple, that might really excite her as well.