Normal Map
The wall itself is just a flat plane. The details are mainly added to it by using normal map in order to reduce the poly count. To create nornal map, open NDO and Phtoshop. Then load the unwraped UV for the plane.Start drawing rectangles and other shapes on the canvas and convert them to normal by using the Convert button on the NDO window.
Continue drawing shapes and edit them until done. Then saves the map.