hmmm... I've purchased that dahlia print in a number of different colors. I hadn't thought about using Shenandoah on it, however. Good idea.
I have quilted large Shenandoah quilts for a couple of friends. As I recall I did a free motion all-over design, much like the above quilt. For a flower, however, I would try something to bring out the individual petals. If you search for "Dream Big panel" you will see several lovely examples of how this particular panel was quilted. My favorite is by Margaret Solomon Gunn -
http://quiltsoflove.blogspot.com/2018/03/bitten.html