Book Reports / How does the painting in "The Picture of Dorian Gray" contribute to the MOWAW? [2]

I have an essay due tomorrow on this subject. I know the painting is very significant in the way that it shows his true self, since it ages, smirks when sybil dies, and shows blood on the hand after he kills Basil. But, then what is the overall meaning of the work in which all 3 of these characteristics of the painting contribute towards?

It is an essay 750 to 1000 words.