The Portrait of Dorian Gray, but instead of becoming vaguely corrupted as he sins, the portrait becomes more pixelated.
That, or it becomes more and more cluttered with pop-up ads.
Dorian Gray, staring at his portrait: I suck ONE DICK on a tuesday and this thing won't let it go.
Flashing ads on the sides of the portrait: HORNY DILFS IN YOUR AREA WANT TO HOOK UP NOW