How would I make custom terrain - based on other games?

For example, World of Warcraft.

If I were to use the skins from the World of Warcraft .mpq file, could I extract the terrain skins from Desolace, for example? How would I go about getting these terrain files in the first place? Next; after the files are obtained, in what way would I format them to create a feasible, good looking terrain skin for Warcraft 3?

I really love the extent and detail to which some of the Desolace terrain skins are done. They may seem incredibly bland (the detail really stands out on a great video card) but the short tufts of grass, varying shades of gray and yellow earth, and luminescent top soil really get my attention. I'm sure a World of Warcraft terrain skin would look amazing on a Warcraft 3 map.

Is this possible and can someone give me instructions on how to do the few things I mentioned?

I do not believe that this sort of action is condoned or allowed by the Wc3C staff. Extracting files from other games and then distributing them with your map is illegal as you are essentially stealing resources from a game that only you paid for, and not that everyone playing your map has paid for.

I didn't realize that. Thanks.