Our emotional sensitivity to shape is demonstrated by the familiar Rorschach (inkblot) test, which was designed to aid psychologists in evaluating emotional stability.
By using the knowledge that some shapes are inevitably associated with certain objects and situations, the architectural illustrator can set the stage for a pictorial drama.
Whether viewing inkblots or artwork, our response to shape is often primitive and subconscious. Some shapes convey fairly common meanings. Square, for instance, frequently utter perfection, stability, solidity, symmetry, self-reliance, and monotony. Similarly, circle may suggest confidence, independence, and/or confinement; oval may suggest fruitfulness and creation; stars could suggest reaching out.
So, you can use shapes to express a emotion or mood, in your architectural renderings. Afterall, isn't that what we are trying to do?