This depiction of Kali and Shiva references the human experience of death. Kali, who represents dissolution mates with Shiva, who represents creation. She drives him mad and he forgets who he is. For a time, Shiva is lost. Such is death.
This is a diagram that describes the symbolism in the Hindu Ganesh symbol. It is one of Hinduism major symbols. It think it is interesting because even the most basic thing can have so many symbols within.