Love this series!
The hardest part is keeping the quilting design as simple as possible so the applique is the star of the show.
Any added filler designs would have to be very simple, rather dense, and in a thread which would be pretty much invisible. (I know some people who fit that description, and want them to be pretty much invisible too!)
Happy New Year!
May your threads never tangle, or your scissors go missing, in 2017!