I modified Shiggs Earth map for my own personal use by redoing europe from scratch and some other areas and placing all extra civs, but i can't really release that on the forums as it's primarily his work.
However it's easy to place extra civs.
Simply download the map you want, download the Civilization V SDK from Steam, open the SDK then the worldbuilder, go into scenario settings, click "+" to add a new civ, then exit the scenario settings window, click edit tile/plot, click on the tile you want and go starting location: civ-you-want-to-star-there. Then save and play it in the game. Make sure to check "load scenario"
Also you'll find many of the maps are missing Babylon as well (more justified because Babylon is in a crowded area of the world).
