Cargo Net as well. Looking into the rear seat covers I found on here.
The ones from Japan? I picked up a set and they are... meh. I thought the fit would be a bit tighter. But I think if I had put them on when the truck was new and prevented the rear seats from getting scratched all to hell, it may have been worth it. So yeah, maybe not a bad idea for your '18!
Other tips from this thread: OEM first aid kit for that little door (bottom right below); front seat mounted fire extinguisher; and I assume you have seen the cooler box storage tray that frequently shows up in this thread (worth it).