Hate to put another spoke in the wheel here, but I think the sashing might actually help to set the blocks off by making them all stand apart from one another, like a collage frame sets off each individual photograph. And since it appears you haven't used the same background fabric for all your blocks, it would be hard to sash them all with the same fabric. I do like the green sashing you've chosen. And the stars in the corners are low enough contrast that they're not going to draw a lot of attention to themselves, but add another layer of detail. You MIGHT consider framing each block with strips of its own background fabric, so they would then float away from the sashing, if that makes sense? Just another opinion.
And no it's NOT a UFO, it's just "simmering". It becomes a UFO when you pack the blocks all away in a bin in the closet where you can't see them. I have a quilt hanging over the rail on the 2nd story landing of our house right now because I have to study it for a few days (weeks) before I decide how I want to quilt it. It's the only place big enough I can see the whole thing!