As with many features of the language, DB provides some very easy-to-use commands for working with terrain, and provides more complex commands for fine-tuning things. The easiest way to create bumpy terrain is to create a matrix, and then randomize it. A matrix is a complex surface constructed of quads. Each quad is called a tile by DB, and you can paint a texture onto each tile individually.
First, you can create a matrix using the make matrix command. This command will construct a simple flat matrix with the specified dimensions, and divide the matrix into the tiles specified using the x tiles and z tiles parameters.
make matrix matrix #, width, height, x tiles, z tiles
Next, you will want to load an image using the load ...