How did you do the photos?
Just walk through the the deep dark woods with a head lamp and look for Zombies. :elkgrin:
It's really easy to do as long as you have a tripod and can control your exposure. I first light the subject with a brighter flashlight and use live view to get properly focused with the lens in manual focus so it stays there. The I set the exposure to between 20-30 seconds. I have the person stay frozen still for the first 8-10 seconds while I light paint them with an LED headlamp then they quickly walk or roll out of the frame. Continue light painting the background with the headlamp until the rest of the exposure completes. That gives you the transparent ghost image.
The longer the person stays in the shot the less transparent they are in the final image.
Sometimes it takes a few tries to get the light balance correct either with less light painting or higher ISO but after a few tries it usually comes together pretty well.
That, or just walk around and look for Zombies, both approaches work.