Yeah, that's the rub...it's in the programming and I don't know anything about programming since Basic went away. Basically the images for terrain are laid out in 16 X 16 grids for rivers, beaches, hills, mountains, roads, and railroads. The programming somehow can chop up the images based upon the 16 grid slices and then plop 'em down in various ways to create the world file. The programming also can choose between sand, grass, and ice base terrains to put the other things on top of. I haven't looked through the forums there for this but I know that civfanatics.com has the largest forums I've ever seen. There are tons of mods there and maybe if you ask some of the folks over there they might help ya out or there might even be a tut. In fact I think I remember a sticky subforum on how to make your own mod and that might be a good place to start.