http://www.cartographersguild.com/showthread.php?t=1769 has a general discussion of the base map
I did an example of the size and placement of the area when placed on a globe. It still amuses me that the southernmost areas of that map are about at the latitude of Moscow. Be sure to click on the images in my post on that thread because the placement and size examples are animated GIFs that fade from the base map to a real-world map.
The map was done using the default terrain generator in Fractal Terrains (it's a simple noise-based generator with no attempt to be "physically correct"). Seeing yet another generic FT map prompted me to write up the tutorial at http://www.ridgenet.net/~jslayton/CGTutorial/ but it was already too late.