Why most Gods are symbolised based on living things.?
we see shiva vishnu all in human form.
the form is for us to look upon and meditate.all forms we see are actually aspect encompassed by God. this is clearly explained in vishwaroopa darshana yoga in bhagavad githa by krishna.(krishna here symbolises the supreme lord.he is personifcation of paramathma).thus, God expressed in human forms/animal forms or other perceivable forms can be understood as God revealed to us in certain asppects for us to meditate, or contemplate; or God revealing a himself in a form encompassed by him that we can pereeive.this is why i think is the reason why God is generally in these forms.
This is because it is easier for the mind to relate to a friendly, human form as compared to abstract formlessness. Sri Sri Ravi Shankar narrates this in the context of Arjuna:
...Even Arjuna did not want god to be in a very powerful form, in the infinite form. He said, “Oh, no! No! Enough, enough! You show me your simple form, your human form!
In the eleventh chapter of the Bhagavad Gita, when Krishna showed his infinite form to Arjuna, he showed his true form. Krishna said, “Inside me you see the sun, moon, stars, fire, earth, and all the elements. The ocean, everything you see inside of me. Close your eyes, I’ll show you with your inner eye,”
And Arjuna got so shaken, he was so afraid, he said, “Oh no! You look good to me as a friend, somebody whom I can talk to nicely, this is enough for me. Don’t show me that! Be a simple form, a human form. I love you in the human form. You come to me in the Human form!...”
Excerpts from a talk: www.dvorahji.com/wp-content/uploads/2013/10/mylittleguru.pdf