If you are willing to dig in, a lot you can do back there.
I have a net made from Paracord, super easy, cheap, and you may be able to find the hard points intended for the ceiling hooks and use something simple like an eye bolt or something.
I have several project threads for the various parts of what went into my rear cargo area. I added lights into the ceiling and rear door, tied into the BCM so it comes on with the door and auto timeout or manual lock on. I have a paracord roof net. LOBO rack with under rack lighting wired in with the ceiling lights so they come on with the door and everything the ceiling lights do.
Then below that is a lock in-out platform that allows access to under floor storage as well.
It was a lot of work, and it wasn't exactly cheap if I were to try to add it all up. But I love the setup, it turns the cargo area into a super useful space. I think what makes me the most happy with it is it's unique and I did it myself, grab ideas from it and other's here with awesome setups, and you should be able to formulate a plan on what you would like to do. It's not as hard as it looks once you get elbow deep into it. (I've had the entire cargo area interior pulled out, twice....)