Using Greeble to place the buildings
By completing this process over and over with different-sized parameters and different region selections, I obtained my mass building effect.
Placement of buildingsI then began placing the buildings I created in Step 1 into my scene. I tried to spread them around in a coherent kind of way, by using some city references.
Use city references for sensible placement
Creating the background buildingsThe image above formed part of the background of my image that was later transferred to Photoshop. I duplicated some parts of the city in order to fill the entire page, and make the city look really wide-spread.