Oh. If you're trying to overwrite it, then just import it over:
ReplaceableTextures\Cliff\Cliff1.blp
If you want to overwrite the first cliff (the village fall grass texture), then import it over:
ReplaceableTextures\Cliff\Cliff0.blp
You will use those paths for the 2 cliffs in your map regardless of what tileset you're using.
As for the actual texture files for village fall, they should be in the war3.mpq under ReplaceableTextures\Cliff\Q_Cliff0.blp and ReplaceableTextures\Cliff\Q_Cliff1.blp