He's found on wooden stands, banners, and carnival games all throughout the level, and is even the basis of some in-game achievements. I know that L4D2 is a little gory and mature for some eyes, so be wary if you want to look into it.
If you want a safe, albeit kinda weird, pistachio themed bonus for the day, take a look at this youtube video where a pistachio gives random trivia to a woman at a bar who seems to have recently undergone some relationship trouble. Okay it's more than kinda weird. But perfectly safe to watch with anyone around. As long as you don't mind people asking "What on earth is this?".
Thanks for reading!