Interesting Herbs, Foods, or Flavorings to Steep into Simple Syrups
You know, aside from the obvious ginger, vanilla, thyme, basil sphere. Seasonal would be nice, too. And let's talk about spirits to mix them with.
Cardamom syrup is used in middle eastern deserts. I bet it would mix well with some of the more interesting rums, and could probably slot into some existing Tiki drinks. Tea, cardamom and cream is a simple chai, making that alcoholic shouldn't be too hard.
Caraway and/or fennel syrup might work in an old fashioned.