Since the quilt is all straight lines, I would try something circular or swirly in a thread color that will mostly disappear into the print of the fabrics. If you want a puffier look, SITD would work, but is harder to do and make look ok. Even a panto in almost any design would work because of the neutrality of the quilt pattern, so in my opinion, you have lots of choices. The quilt is very pretty, love the colors.