How to add a new terrain or feature to a mapscript?

[CaptainLost]

I've been getting into python lately, with the help of a bunch of very good tutorials, and I decided I want to try to learn some mapscripting.
Problem is, apart from Sirian's "guide" to mapscripts there are 0 tutorials about them on the site.

Would anyone be willing to explain to a relatively nooby python modder how to add just one new terrain or feature - something completely new, like a volcano or cactus - to a mapscript?

From there I can work my way up, but right now I don't even know where to start other than swapping out terrains that already exist for new ones.

 

[vincentz]

for adding terrain to maps, try to look at the swamp here :
http://forums.civfanatics.com/downloads.php?do=file&id=10820

and for the features, look for the oasis. Most mapscripts will put any feature you add to the xml on the map.