The standard tilset is a simple tileset that contains only one layer. The tile-types in this set are the following:
From the picture below it becomes clear why we refer to WCS as a tile-based game. The maps in the game are made by cleaverly putting together sets of these tiles. Note that for each tile an attribute can be defined that indicates if the particular tile can be passed by "ships, planes or automobiles"
For the WCS-project a map-editor is available that can assist you with creating maps quickly. The map-editor can be downloaded from the project-page.