Here's my thoughts.
SID around blocks to anchor everything.
Loose stipling in white background
Echo in rectangles, squares, and triangles
Loopy design or feather wreath in red squares.
You are right that an over-all would not look good. I did a similar quilt and had an over-all done (only time I sent one out to be long-armed) and am sorry I did that. Sure wish I had done my own quilting.
Best of luck, the quilt is lovely.