The glacier tile set will replace your winter tile set. The mountains will be replaced by glaciers, the rest will be unchanged. There are no changes in the gameplay (no new AIs).
To install it, simply run the exe file in your War2 directory and answer all questions with "yes".
This tileset has been made by Cameron Vine.
To get your old tileset back, either copy maindat.war from the CD into the war2\data directory or make a backup of that file first.