This is a great counterpoint to the traditional Judeo-Christian view of man: "Little less than the angels have you made him" (Ps 8:5). If you want an interesting counterpoint to what Winston sees in the mirror, think of the statue of Michaelangelo's David. This ideal of the male form is presented in this statue, man as the direct inspiration of God. It may not be too far a stretch to see Winston as the creation of the "new" god, the state. Instead of the idealization of the male form, complete with all the potential God had put in it and which the Renaissance and subsequent years saw it in, we have the shell of a man. Instead of muscular, he is "skeletal." But he is a perfect creation of the state, a being with almost no humanity, almost no will, almost no strength to resist. There are no more men; if Winston believes he is a man, he is the "last" --- and there is not much promise in him.
In the humanist tradition, the statue of David was the ideal; in 1984, skeletons are more useful.
When Winston say that he believe he is a man, O'Brien says if you are a man, you are the "last man." He then orders Winston to undress and look into the mirrors. Winston sees a
“skeletonlike thing” and a “creature” to suggest that the Party has succeeded in stripping him of his humanity. The color “gray,” which describes Winston’s body, might more traditionally be reserved to detail the deterioration of a corpse."
O'Brien asks Winston is this the "man" who will overthrow the Party? He makes the point that the party can't be overthrown by anyone ever because what has become of Winston will happen to anyone who tries.