...draw a single texture in each square of the terrain...
no. But you could use a shader (what else
) to place different textures on different spots, but you are restricted to 16 textures per render pass. (Actually 15, because one of the textures is used as blendmap). This is done with a bitmap of the same dimensions as the terrain (example: the terrain is 256x256 cells wide --> the texture is 256x256 pixels wide). Every pixel is one terrain-square. You can now use 15 different colors to draw the 15 textures.