Going by the front covers, we've seen a jungle, then cold, icey mountains and lastly the desert. Landscapes that remain then are the sea, the city and grassy plains.
I say something involving Atlantis for Uncharted 4 is a good idea! Put the sea on the cover. Then, after that, take Drake to a couple of ancient cities, like Rome for Uncharted 5 and finally, your idea of the Holy Grail (the epitome of treasure) in Uncharted 6.







