Detectives issued the still pictures today (Friday) and appealed to witnesses to the attack on October 30 at Wakefield Westgate station.
The assault happened just before 11pm, when four friends left a train and waited outside the station.
Two men approached them and pestered them, before kicking, spitting and striking the victims with bags.
The man then assaulted a bystander who tried to help them.
Investigating officer PC Katherine Purcell, said: “This was an entirely unprovoked and vicious assault and we are working tirelessly to trace the two men responsible. “Everyone has the right to travel without fear of being a victim of crime. This behaviour is inexcusable and I would encourage anyone with information to contact us as soon as possible.”Anyone with any information is asked to contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 173 of 02/12/2016. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.