Ghost Face

Start with a background color you want to use, and paste in the face you want to use with your image.

Desaturate the layer with your face so that there is no color by going Image>Adjustments>Desaturate.

Now, hit Ctrl+L (Mac: Command+L) to adjust the levels, here are the settings I used, but you can play around with the sliders until you get something that works well with your image. To the left is what I got with those settings.

Now go to the Layers Palette and set the Blending Mode to 'Screen' so that only the white comes through and black isn't visible. Also, we don't want the neck, just the face, so grab the eraser, set the Mode to Pencil so that it has hard edges and erase the neck, zoom in, it will help.