Caffeine free teas can be comprised of a variety of components; flowers, fruits, herbs, roots, & spices. These are actually called tisane if you'd like to be specific. Tisanes are herbal infusions that don't include the camellia sinensis plant, so they are not considered 'true teas'.
You'll find a large variety of tisanes available for purchase or special order, as well as a few individual ingredients you can purchase to add new layers of flavor to your blends. Try mixing and matching something new!