My final touch is going to use these artificial berries (also found in the dollar store) to give some texture and visual contrast.
In this case, less is more. I'm just going to put a couple of stems into this arrangement. I really like the effect that a little white in the berries manage to pop out and give contrast to the deep colors.
Tuck the second stem under the pumpkin lid, burying it a little deeper than the flower heads.
The overall design is very pleasing. Rotate it around, seeing if you need to add anything else. Fall arrangements always seem more clustered, allowing the rich autumn colors to blend rather than letting too much green from the foliage show.