I picked up a carpet remnant, cut it to the right size of my wife's Pacifica, then brought it in to the carpet dealer & had the edges bound. It covers the entire back area with the seats down & looks great. Plus the dogs can grip it easily without sliding around as we turn the car.
I haven't made the same move on the Nitro yet. But the lack of any cover for the back of the seats is about to push me there.