The 25-year-old victim was walking with a friend along Briggate when a man approached him and started a verbal altercation.
He was punched repeatedly in the face, suffering two large fractures to his jaw.
Detective Constable Lee Thimm, of Leeds District CID, said: "As part of our ongoing enquiries into this offence we are releasing these CCTV images of a man who we would like to identify and speak to in connection with this assault."
Police say the two images show the same man, despite his differing appearance.
The offence happened at 3.20am on September 30.
Anyone with information is asked to contact Det Con Thimm at Elland Road police station via 101 or Crimestoppers on 0800 555 111.