Backbends are not poses meant for expressionism. Backbends are meant to understand the back parts of our bodies. The front body can be seen with the eyes, but the back body can only be felt. That's why I say these are the most advanced postures, where the mind begins to look at the back.
B.K.S. IyengarFocus on keeping your spine straight. It is the job of the spine to keep the brain alert.
B.K.S. IyengarWhen the restlessness of the mind, intellect and self is stilled through the practice of Yoga, the yogi by the grace of the Spirit within himself finds fulfillment.
B.K.S. IyengarMind is the king of the senses; breath is the king of the mind; and the nerves are king of the breath.
B.K.S. Iyengar