Sticking with modifying human figures for the time being. This effect is intended to create a predator like camouflage effect, though after seeing the results, I think it might work just as well for creating ghosts. I used this tutorial.
For my stock, I used Tecumseh Stock 12 by mountainsidestock for the background. And when it comes to the image, I feel I would be doing all of my fellow writers a disservice if I did not show them the cover art perfection that is Jason Aaron Baca.
Makes a nice haunting effect that could be easily composited into another image.