Great quilt and perfect corners. As for borders I really like the blue gray leaf color.
After looking at this quilt I might suggest taking three dark colors from the quilt and cut them into the same size blocks as in the quilt and sew them into strips for the border like F-1, F-2,F3, F-1 F-2, F-3, etc. Just an Idea.
Also I would first add a white border the same size as the sashing then add the finish border.peace :D
Or! Take three blues, greens or browns from the quilt and do light , med, dark around the quilt. I think I like this better!