NTG. I'm sorry to say your greenhouse looks empty. I have mine stacked from floor to ceiling. It's only 6' 8' and I have two mini greenhouse 4 tier stands, and a potting station on one side and on the other side a 6' two tier staging. Round the top of the greenhouse like you I have shelving running round. Having said that I am also storing a number of tools in the greenhouse as well.
I do have the advantage that my greenhouse is secure in my back garden. If it wasn't then I would not have so many things in it or be over wintering so many pot plants such as oranges. I also have two electric propagators and one non-electric working in there at this time to grow all my annual bedding plants.
Jax