I just figured I would give this a shot I may update it in the future. I added the Colonization art defines for terrain art and added the marsh to the terrain infos. Then I also updated the map generator script and raised the percentages for the marsh and plains.
Anyway I hope it might be of some interest and use.
Updated October 5, 2008
Colonization Base Land Terrain including Marsh for 2016-10-05
Colonization Base Land Terrain including Marsh for