Freddy's scars have changed in every movie.  David Miller was the first to create the burns on Freddy's face modeling them after a pizza.  He created big wounds all over Freddy's head.  On Nightmare 2, Kevin Yeager got the Freddy make-up job creating a tight / pulled back skin look.  The wounds were small with a melting look.  On Nightmare 3 Kevin Yeager returned, building upon the Nightmare 2 look.  Nightmare 4 is almost identical to Nightmare 3 except the wounds are just slightly bigger.  The First Season of Freddy's Nightmares looks exactly like Nightmare 4.  Thus being the last time we see Kevin Yeager's make-up.  Nightmare 5 saw the return of David Miller going back to his pizza look with an element of healing to Freddy's burns.  In Season 2 of Freddy's Nightmares and Freddy's Dead David Miller took the healing of the wounds a little bit further.  With Wes Craven's New Nightmare, David Miller created a new look for Freddy giving his wounds kind of a sliced look.  And in Freddy Vs Jason Freddy's burns went back to the Nightmare 4 look with bigger wounds.