Ars Technica is passing along word that Left 4 Dead 2's original promo art (and presumably, the game's eventual box art) has been censored by the ESRB. Around the time of the game's announcement, the original art pictured the hand from the first game's box art with two fingers held up -- the other three digits had been severed off like the thumb from the first.
New art has been revealed, however, that shows a hand simply tucking two fingers behind the palm. According to Ars Technica, Valve was told by the ESRB to change the image, which Valve has posted about in the company's typical snark-filled fashion. Official box art for Left 4 Dead 2 has yet to be revealed (though the file is named "L4D2_Box", so there may be even more digital manipulation in the works).
This wouldn't be the first time that the box art for Left 4 Dead has been changed. In October of 2008, Kotaku reported that the German version of the first game received a similar hand makeover, with the thumb being tucked behind instead of digitally gnawed off.
For further details, including before and after pictures, check out Ars Technica's post.