We are not sure if Valve is just pulling our finger (pun intended) but in their latest blog post on the Left 4 Dead site they talk about how they created the image of the four fingered hand for the box cover to their zombie co-op shooter. Valve didn't want to use Photoshop so they got one of their artists, Andrea Wicklund, to bite her thumb for reference pictures.

Valve then claims the ESRB ratings board didn't care for that kind of dedication to the art, saying they "cited some fake-sounding legal loophole about it being illegal to take pictures of people biting off parts of their hands." For the upcoming sequel Left 4 Dead 2 Valve says they simply tucked in two fingers for the box design (which you can see after the jump). Valve does say " . . .it took lopping the fingers off two staff members' hands to get the lighting reference perfect, but since those didn't appear on the box, we think we're legally in the clear." We think they are joking.