[Daynarr]

Since you mentioned it, is there any site where you can find Dom I maps? I would like to try them in Dom II editor.

As far as editor goes, you can't do EVERYTHING in it but basically it goes like this; you make a map is some graphic editor program, load it into editor, set up all the basic stuff (like neighbors, etc) then edit in text editor to add special commands for map (like allies, specific special sites, specific population etc.) there is a document in PDF that will guide you through mapmaking.