Well, the main part is done now!
I ended up using one less color than I'd planned, because it blended into the fabric too much when stitched. I think using the blue-purple shade again was a good idea anyway, as it further reduces busyness.
Typically, I've completely changed the way I'm doing the background. Instead of doing another fill pattern, I'm just using straight lines. I *think* what I'll do is have all the lines pointing to the center of the star (it will end up being a perfect square)
So the corner pieces will have diagonal lines slanting inward, the triangles on the top and bottom will have vertical lines, and the triangles on the side will have horizontal ones. Is that clear? Does it sound like a horrible idea? Have I gone mad with power?!
I sketched it out and it looked good, but haven't changed the proper pattern yet.