I don't know what to call this... I've called it "Ancient City", "Ruined City", "Lost City"... Whatever. I toyed around with these tiles in the past, and I'm taking another stab at them, thinking about what might constitute a full 'set' of tiles:
I think of these tiles as terrain plot hooks - I'm not looking to actually build a whole ruined city (not yet at least). I'm looking to have a little bit of civilization peeking through - enough to make a player realize they've stumbled onto 'the spot' where something needs to go down. I like the dried-up and murky fountains... I'm going to try to add some leaves to the water in the fountain. The other two tiles... Hrm... I need to tinker with the grime on the bricks - they stand out too much. I will be cloning some grass in between the bricks a little, and I think that will go a long way.
Update: Someone requested "brown stagnant water" rather than the "mossy green" one. Here an attempt: