I'm afraid that the blocks with a light background would get lost with cream sashing. I love the idea of setting the blocks on point, but I would never cut any apart to use as setting triangles. I've never had a problem with stretching when setting blocks on point. I like the idea of using blue or the lighter brown to match the blues and browns in the blocks. And definitely use cornerstones, perhaps the darker blue if using blue sashing, darker brown or brick red if using lighter brown. Audition anything before you try it, at least with a few blocks. It's going to be a lovely quilt.