I defaulted to feathers, an elegant choice when no other theme seems obvious. The outside borders are a reverse feather design, the large top border and the similar blocks forming the central cross pieces received a feather curl. It's hard to see with the neutral thread but any other color might have been too distracting from the intricate piecing.
Three different feather designs for the various border areas
I was then left with a T shaped area at the outside end of the cross pieces that lacked quilting and considered several options before I settled on crosshatching. I am quite pleased with it, honestly, I was rather tired of all the feathering!
View from the back shows the feather curls and the space I needed to fill between those and the borders.
Quilting always shows better on the back and makes a whole quilt effect for a reversible quilt!