This challenge was more difficult than it looked at first sight.
I originaly thought of changing all four president for the Beatles
but when I saw how difficult it was to get the correct stone texture for
just one face I gave up the idea.
I decided instead on JFK and added it as follows.
Found a suitable pic on the web cut and pasted the face onto rushmore pic changed size with
transform >scale took the brown colour out with desaturate. I adjusted face and hair colour
with adjstment>color balance added noise for texture intensified shadows with burn too.
To get closer to the stone colour I selected GW's face pasted
it, cloned over his featured put it over JFK's face
and lowered the opacity to 45% Far from perfect but the best I could do.
photoshop 7 throughout.