The scarecrow would be perfect(it's an uchi PWP I think).Also,the rack of rice,firepit,water well,water pump,torch,windmill....all of the rustic looking PWP's might be good.
Try visiting http://dreamingofacnl.tumblr.com/tagged/fall
You can see autumn themed towns and get some inspirations.
As others have said the log bench in my opinion gives a great nature feel.
I think that you could also add a well near the cluster of villagers above your tree.
Planting sweet olives is a good idea as they bloom in fall too.
Have fun!