I've used albizia jullibrissin bark/flowers, it was nice, had visions of middle eastern symbols. I've used chamomille as well, for me it adds an ancient Egyptian element, visions of Egyptian archetypes. I like to add some Passiflora to the rue also. Yaupon or Yerba mate are possibilities.
The other day I made a brew with rue, desmanthus and used crossvine as an additive, then drank it in the woods. Desmanthus and crossvine are both native here and I felt a deep connection to the forest.