The pose Agent 47 makes while exiting an elevator early in the film by facing forward and crossing his arm over his chest while holding his pistol is reminiscent of signature promotional images used throughout the Hitman video game franchise but the "blood on the sleeve" is from a cover of Hitman: Absolution.
In the month's prior to the movie's release, 20th Century Fox and IGN Entertainment launched a social media campaign in order to find Hitman Agents 1 through 46. Contest entries, which were mostly comprised Agent 47 cosplay photos, were judged by a panel and winners were officially given numeric designations in the Hitman canon.
The idea of a young girl who has assassin-like abilities (like super reflexes and freeing herself from her ties) who is also wanted by an evil corporation is taken directly from the plot of Hitman: Absolution (2012).
The mid-credits scene where Quinto's character wakes up with white hair and a pale complexion is a direct reference to the video game Hitman: Blood Money as the Syndicate assassins in the game are all albinos with white hair and pale complexion.