The desert tile set will replace your wasteland tile set for PC users. The trees will be replaced with cacti, the ground tiles will be replaced with sand tiles, and the critters will be replaced with scorpions. Just unzip the contents of the desert.zip file into your war2 directory, and double click the desert.bat icon. The next time you start a PUD with the wasteland tile set, you'll be playing in the desert. I "authored" the tile set, the cacti were done by rex sutton, and warlock did some touchups, and converted the scorpions from the war2alpha.
We hope you enjoy the new type of gameplay that we have all worked hard to provide you with.
To get your old tileset back, either copy maindat.war into the war2\data directory or make a backup of that file first.