Well, you can look at the ".GC2Map" files located here"Data\English\Campaigns" for an example.  They can be opened with notepad or a similar text editor.

Alternatively, if you have Twilight of the Arnor, you can use the Map Editor program that comes with it.

Even if you don't have TA, you can manually make a .GC2Map file.  Like I said, it can be opened with notepad, so just make a copy of one and change some values and resave.  You know, play around with the values and see what happens.

Obviously, it'd be better to have a graphical tool that does the manual editing for you (ie. the Map Editor that comes with TA), but in the mean time you could get by with manual edits until you save up enough coin to buy TA.

Happy Modding,
~C

that wont let me download it, it always cuts me off at like %10