As
@Danarch said, you can flip the image in the setup. From your pictures, you could mount it on the disk behind your wheel. It wouldn't be perfectly centered, but it would still function just fine.
Personally, I'd probably mount it on the third brake light, but I'd do a test first. Slam the tailgate. If the third brake light vibrates, your image quality mounted there will be garbage. If it ends up mounted there, you can adjust the angle of the image by swiping up and down on the mirror. My camera is mounted above the liftgate. When backing, I often swipe down. Makes judging distances really easy.
Another alternative would be mounting it on your rear bumper, under the tire. The hitch and tire would protect it if you do any trails.