A simple 16x16 terrain tileset. This is designed to work in color AND in monochrome.
In making this, I condensed all known biomes (terrestrial, aquatic, air, space, manmade, transitional) into 26 tiles. This allows a given tile to define multiple different types of areas/terrain, and it allows you to come up with your own meanings for these tiles, rather than having to memorize a legend. Some of the tiles are obvious and some are not; this is by design.