I like it the way it is. Have you considered putting a dark green in the center. These are flowers, and the flower would put the "stem" area in shadow, so whatever goes in there would probably need to be darker. BTW - not sure if it was intentional or not, but where the outside corner triangles meet in the inside of the block looks like it was fussy cut. Upon further closer look at the four pieces of the block - ALL of the green triangles appear to have been fussy cut. Wow! Anxious to see the whole quilt. Great fabrics and great colors.