Frank Sinatra was an American pop figure, he rose to fame in the 1950's and is considered as an influential celebrity of the 20th century. Frank Sinatra's portrait can be found at Saint Marks. Rockstar intentionally referenced Frank, to highlight his criminal controversies, most notably with the Mafia.
Vice City Mafia
Frank Sinatra had controversial ties with the Italian and American Mafia. Willie Moretti, Mafia lord, helped him get breakthroughs throughout a particular phase of his career. Sinatra is also known to have attended the Havana Mafia conference in the year 1946. He had strong ties with infamous Mafia lord, known as Lucky Luciano. He was allegedly, the best friend of the American Mafia lord, Sam Giancana. His controversial and professional links with the Mafia, is regarded as a subject of contention for him. It is highly likely that Rockstar placed his portrait at Marco's Bistro, to reference Vice City Mafia and supposedly his tendentious links. Players have speculated that he is related to Forelli Family and their infamous Mafia nexus.