I think that would look good. Personally, I would add the green fabric and put two arrows pointing downward to make it look like a mirror image of the other arrows you have at the top pointing up. With that spot being small, a pin wheel might make it look to busy.
Adding the pinwheels to the bottom to make bigger would look great. I would do three small blocks of them.
Can't wait to see what you decide on. I am sure anything would look great! :)