Another wildflower to consider - Maximilian Sunflower (Helianthus maximilianii) or it's close relative, the Sawtooth Sunflower (H. grosseserratus)
Speaking of thistles -
and Goldenrod -
and N E Asters -
(in my garden)
Purple Coneflower and American Bellflower (an annual wildflower) are also worth consideration. (Good pics in the database of these two)