DVD Cover as pictured on IMDB
Correct me if I'm wrong, but I don't believe Sinatra ever wore that helmet. Neither did he carry a machine gun whilst apparently leading the guys into battle. His whole schtick was that he was an amoral, anti-war slacker who didn't want to take sides.
I presume it's a contemporary painting, and that the producers figured they'd better portray him as the action hero of the movie.
Awight we're The Daamned we're a punk baand and this is called Carn't Be Appy T'day!