Ancient Mesopotamia should really get more representation in the game. I would love Sumer, as arguably the most important, and they could really take Sumer in a lot of different ways to make it quite distinct from Babylon. (Both Babylon and Sumer have been in the same civ game in the past, more than once even, so the overlap with Babylon isn't really a problem. Plus, Sumer is a two time missing legacy civ). There is something to be said that they were already half-heartedly implemented in the Wonders scenario. Still, this doesn't detract the fact that ancient Mesopotamia really deserves at least one more rep and I would love to see either Akkad or Assyria if Sumer is out.
Also, I really wish they made a nice static leaderhead for Sumer in the Wonders scenario (like they did for the Viking Scenario). It would have really made it simple to mod in a high quality version of the civ based on the scenario. Instead they used Harun al-Rashid to represent Gilgamesh, which was completely absurd aesthetically. Darius would have made more sense, but still been off.