2. Add Dimension
Add a second side to each building to convey a sense of depth. Do this by drawing a vertical line shorter than the two lines for the front of the building.
Connect the side line to the front with a diagonal line. Then lay down evenly spaced horizontal lines on the front surfaces of the two buildings near the middle of the scene. Place another building in the left part of the background with a tall, narrow shape that has steps on one side.