On the second wall, which is opposite of where Diana is looking in the original photo, we can see what looks to be the arrival of Steppenwolf, although I see no horns. We can see the Amazons arriving with bow and arrow ready to battle it out. Surprisingly enough, we see more Tribes of Men standing next to what is obviously the 3 motherboxes we are told about in the History Lesson. I have no idea why the drawings are separated with inscriptions so, again, I leave that guessing up to you.
With this wide shot image, we can now see how the 3 walls come together, with the first wall now aligning on the right of the image. That would mean behind this photo that was taken, is the wall that Diana is observing.