Sounds like you have plenty of quilting on it already. If you have room maybe you want to put one more echo. in the smallest heart.

I've only pieced the top and basted the sandwich - I've not quilted any of it, yet.

Okay, I think I understand now, you want to know how to quilt it after it's sandwiched, I'm thinking that since there's no sashing on the top and the blocks are 9 inches, how about a decorative stitch on the half inch of the block that's free of the applique? After quilting, I would use a chenille brush to "rag" the heart edges.