This is a photo of a group of LARPers getting ready for a game. I used Photoshop to blur the background and bring the focus on the gypsy and the dark-elf in the center. Here's a link to the original photo: [link]
If I remember right, they got it at a professional costume store. It's a power often used to represent dirt on people's faces in plays. I don't remember the exact name of the stuff, but if you went to the LARP Alliance website and asked about it on the message boards, I'll bet someone would know.