What message does Oscar Wilde send to readers in The Picture of Dorian Gray?
Oscar Wilde is not a moralist. As a follower of Pater, and as an aesthete, he believes in "L'Art pour L'art", or in art, for art's sake. This means that his work does not attempt to judge nor criticize, but to create a conduit of beauty.
However, there are parameters that are stated subtlely in the novel which may have been added by Wilde towards the third revision of this publication for the sake of saving himself from some harsh, puritanical criticism.
Among these parameters is the message that there is always a need for some form of control, even in an era of hedonism. Lord Henry and his ideas of seeking and searching for new sensations are laid upon Dorian as mainly that: ideas.
It is Dorian, his own ego, and his indescribable pride which makes him petulant enough not to realize that there is a limit to everything: even to experimenting with feelings and sensations. He, however, lets the worst of it, literally, get the best of him, rendering him a victim of his own vulnerabilities. In all, his strongest trait, which is his ego, becomes his weakest link.
Ah! in what a monstrous moment of pride and passion he had prayed that the portrait should bear the burden of his days, and he keep the unsullied splendor of eternal youth! All his failure had been due to that. Better for him that each sin of his life had brought its sure, swift penalty along with it. There was purification in punishment. Not “Forgive us our sins” but “Smite us for our iniquities” should be the prayer of man to a most just God.
This is why, at one point, he finally has enough of the insane occurrence that is happening to his portrait. He realizes that there is no hiding from one's sins: they manifest in one's life, or in one's appearance, in one way, or another. Dorian IS proud enough to realize that his picture still bears the reality of his life. The face that looks back at him from the picture is his own face, the way it really is. The disgust over what he sees prompts Dorian the wish to destroy the picture. He destroys it because he wants to destroy his ugly reality.
Hence this is the one message that we could sift from the novel: sins do become us, whether we hide them behind the masks of a beautiful face, or a hospitable countenance, or good manners. Our demons chase us and manifest upon us. In Dorian, they manifest in his picture, for it could not manifest in his actual appearance. However, his actions and all the ruin that he causes are enough proof to sustain that evil is as evil does, and it gets found out in the long run.