Yup, there are tie downs back there (near the liftgate on the sides, and up front near the seats) that you can use to strap down stuff.
I ended up pulling out the double-deck system entirely to put in a new 'floor' with a pull out table and a drawer system that is strapped in with turnbuckles to these mount points.
While I set this up so I can take the drawers in and out, I nearly never do, it's just too convenient having them back there since this is our main adventure vehicle. Heck, even the fridge gets used for grocery trip runs.
You can see where the mount locations are here, I reused the tie downs and just got longer bolts.