first off, maps with randomly placed tiles are ugly, round them off or something. Try and make them look realistic unless it is a FFA map.
There are 2 approaches on cliff making.
1. select an area, hold shift and start clicking using right button on mouse.
2. make a bmp of your map, color in elevations (black and white). The lighter the color the higher the elevation. Set a light color by a dark color and you have a cliff. Save it as a greyscale, 256 color(8bmp). Open TE, File>import