This is a beautiful sampler. I have LA so my suggestions will probably be much more than you want to do but I tend to always SITD on samplers to help emphasize all the piecing. Then I usually come up with several FMQ motifs I can repeat throughout the quilt to bring continuity. If this quilt came to me I would probably do some sort of feathers in the white areas, changing them up a bit to fit the spaces and curved crosshatching in the setting triangles. I can't see enough of the borders to make a suggestion on the borders.