Start with, in this case, a face. I like to go with a self-portrait. (Others might not actually enjoy seeing themselves grapically ravaged by digital disease.) A black & white image is preferable. Background should be completely black with only the face highlighted. Contrast is important for this technique. Pick a texture that also boasts a fair amount of contrast. Pictures of decaying walls and peeling paint are some of my favorite subjects. (Make sure to convert original b/w to a color image when working with color texture.) Apply texture over entire image and use the "Multiply" filter. (Run through the other filter options in Photoshop if this doesn't seem to be the optimal filter.) Use Photoshop's "Variations" feature to pump up one of the colors. (In my "Leprosy & Me" example I increased the RED. Then go back, using the history brush in Photoshop and paint back in the original CYAN and WHITE highlights. Finally repeatedly use the UNSHARP MASK filter to SHARPEN edges of "stucco" to get more depth into the crevices and cracks.