Here are a couple of drawings that I did as part of my story-boarding class during Spring'07 at SCAD. We had to come up with a rough story concept and design an imaginary place for that idea. It is very difficult to design something without any reference at all. The best thing to do is to study references for all or some elements of the environment and add your creativity to it. References help making the environment more believable when all the elements are put together. Hence it is very important to study real life references, be it a drawing or an animation piece.