This will get you larger random maps
EDIT: version update and link to packaged mod -- rlane48
See a bunch of people asking for larger random maps, so I've been playing with making some. The code block below can go in your mods folder and you can try out two larger map types...
The first increases the size of the map, but keeps it relatively square, the second (huge/irregular) creates irregularly shaped continents by drastically increasing the map's water percentage. The huge maps pull in some big areas with fertile rivers and such that allow for city crowding (1-3 cities), which I suspect is due to the stamps they are importing. And I've only play-tested the first, and then only for a couple hundred turns. I had fun with them so far though -- I had ten players going and there was LOTS of room for expansion and exploration.
I haven't playtested the irregular maps, but they look interesting. Attempted to post a picture of one of these in a link at the bottom of this post.
Anyways, this is a start -- try them out. I'll keep working on refining them, including maybe getting into stamp creation.
You can download the files here: http://fallenenchantress.nexusmods.com/mods/18/
Please see the README file included in the zip for installation instructions.
Many thanks to:
Matopicus -- 55% water suggestion on the Irregular maps
Ragnin -- Helping me out with the City placement restrictions
Heavenfall -- For the tip on how to include modded ElementalDefs.xml