Read Poe's The Raven and thought about different bird -- red winged blackbirds. Growing up, we had a particularly vicious territorial red-winged blackbird that took over our backyard. It swept down on anyone who tried to take the garbage down to the cans by the alley, not that I needed an excuse to avoid this chore, as this particular chore never fell on me.
I usually think of ravens as an omen of death. The raven, however, also symbolizes protection, initiation and healing, and the death of one thing to bring forth another (to the Celts). Attributes include eloquence. Native Americans associate ravens with a positive change in consciousness and with shape shifting. Change seems key. Complicated birds.
Apparently, ravens live in the Tower of London. Their wings are clipped, lest they were to fly away and disaster were to befall England. Poor birds. Wonder if they want to shape shift.
The association with shape shifting could let ravens operate metaphorically in an artwork to denote formal shift, except that in an image the shift can be seen as one of the set view, rather than a difference in form itself. A square rotated to be viewed at its edge becomes a line. A cube viewed dead on from one side is a square. Perhaps what occurs with the shift between life and death, conscious and unconscious, is simply a shift in the view.