First find a picture. I got mine off google just to use as a example. Once its in photoshop take a soft large black brush and brush out the background leaving an effect similar to what I have in the one I made
Note: You'll also want to use a low opacity brush to make the edges look kind of dark...like shadows on the face
Step 2: Find a cracked or Grunge texture
You can locate this on google as well. Put it over the picture in a layer above it and set it as multiply. Then take a soft eraser or "chalk" brush and erase where the black is and where the eyes are
Step 3: Erase the mouth
Ok heres what really makes it a cool picture. Take the clone copy brush and go back to the layer with the face on it and alt click somewhere near the cheek and then paint down on the mouth, this will erase it and replace it with the texture from the cheek!
Step 4: Finish Up!
Now take some various grunge brushes and paint about, adding to the effect. When finished save as both a jpg and a psd file that way you can go back and edit, just in case!