I just quickly threw this together. Does it help? I will try to fill in some of this later such as the specs on the image formats, and the specific steps in the map editor.
Basic How-To maps:
The image can be anything from anywhere. The map generator can be used. You can modify the colors and much about the generating but they can always stand some manual improvement. Or a map generator from another game might be a good starting point. Or a satellite image, a drawing, change the colors all to monochrome or sepia to get a drawn parchment look, even a picture of a famous movie star can be a map.
The Image format must be .rgb or .tga (insert specs) when you are done with it. The map info file must be plain text (ascii) and have the extension of .map
Image
-> change all white (255,255,255) on the image to something else. Maybe grey (250,250,250)
-> add ONE white pixel to the image for each province (where the flag pole will sit)
ImageOptional
-> add red borders to help the map editor find proper neighbors (you can change the color or delete them later)
.map file
-> add neighbor commands (do not need 2-way)
-> add terrain commands
use of Editor
-> create a bare .map file then load it into the Dom3 Map Editor under Game Tools
-> have it guess at neighbors (it cannot guess at terrain)
-> edit neighbors
-> edit terrains
.map optional:
-> set certain provinces as no-start (or set only the start provinces)
-> add names for provinces
-> set Victory Points for certain provinces
-> select provinces for special considerations on random magic sites
-> add magic sites for affecting temperatures or scales
-> select poptypes for certain provinces
-> select guardians for certain provinces
-> place forts, labs, temples
-> select gods, magic, scales, alliances for specific AIs
Mapping Quick Reference List
http://www.dom3minions.com/docs/map_qref.txt