I don't know if you notice it or not, but down in the midst of the purple text, you can see a bit of blue haze between the third and fourth characters if you look closely.

Also, the red spray outline around the orange text on the right looks very uneven, very unclean. In other words, it doesn't look professional.

Therefore, I conclude that it's a hoax. Lookin' around, I haven't found anything concrete to rebutt the validity of the image, but my guess is that it's just another forged rumor.

EDIT: If you copy-paste into Paint and invert the colors, it looks more unclean there. And the back of the girl at the bottom right looks even more fabricated. It looked out of place to begin with. . . And also take note of how a couple of the letters on the right side are off-center.