Beautiful quilt. I would make a small border with a similar medium or dark blue fabric, maybe using something used in the quilt if you have enough fabric. Then have a very small folded fabric or corded accent border of yellow, then followed with your flowered blue fabric for the outer border.
I would also use this same flowered fabric for the binding ic you have enough. If not then maybe make the binding out of scraps of all of the fabrics used in the quilt top.
It would appear from the picture that all the fabrics you have used so far are prints. With this in mind I would stay away from using a solid but use another print
Hope this makes sense to others.
Pam M