I made a mask of the body without the eyes/hands/brows/mouth, made the body black and white. Applied that mask to whatever image I want to swap in, and set the layer to overlay. It kills the saturation a bit, so I put a saturation layer masked to only the body. Sometimes you need to make the image brighter too, like the mao face.

I probably should have tightened up the mask on the shaded side of the body, but w/e, viewed small its fine.

Edit: looks like this. Group 1 is whatever image I want to swap in.