It was known far in advance Henry Cavill would return so why wasn't Superman included on the Justice League movie poster and other promotional material? Henry Cavill had something of a long road to movie stardom, especially when it came to major franchises. He was up for the title role in McG's Superman: Flyby before the director left the project, he came close to playing James Bond in Casino Royale and was considered for the role of Edward Cullen in Twilight.
Cavill's determination paid off when he landed the Superman role in Man Of Steel, which would be the first entry in the DCEU. Cavill would return to part for both Batman V Superman: Dawn Of Justice and Justice League, though it's currently unknown if he'll play the role in a future project. While the reception to the movies themselves was often mixed Cavill brought a real charm and physicality to the character.
Related: DC Are Making A Mistake Leaving Superman Behind
The ending of Dawn Of Justice saw Superman slain by Doomsday, though the final shot of dirt floating slightly above the character's coffin indicated he would return. The character was later included on a poster for Justice League shown at Comic-Con in 2016, yet the marketing material that followed went out of its way to exclude Superman, including this Justice League movie poster released just prior to the movie's debut in cinemas.
From one perspective, this marketing tactic makes sense. Superman supposedly died in his previous adventure with Suicide Squad also making a point of the world mourning his loss. While fans expected his return, it wouldn't necessarily be for Justice League. That said, it was also blindingly obvious Henry Cavill would be back. In addition to featuring on the aforementioned Comic-Con poster, he was photographed in costume on the set, he was on the promotional campaign - where he had to play coy about even being in the movie - and there was the now infamous mustache debacle.
The star had grown facial hair for Mission: Impossible - Fallout but was unable to shave it for Justice League reshoots, leading to his upper lip being distractingly airbrushed. These reshoots had been extensively reported, so there was no real mystery about Superman's return, so why exclude him from the Justice League movie poster and assorted material?
Henry Cavill would label these lame attempts to build suspense about his involvement "ridiculous" considering everyone knew but also admitted introducing some mystery was important. While nobody from Warner Bros has officially commented on this campaign, that appears to be the main reason for it. Superman's absence from marketing and the Justice League movie poster got fans talking and it could be justified that since the character is supposedly dead, they would have spoiled his return by including him.
In Justice League, Superman's absence for most of the story makes sense considering he's easily the most powerful hero. He's the reason the heroes succeed so the build-up to his triumphant return proved worth the wait. That said, a more savvy marketing campaign could have played up the mystery surrounding how he returns, instead of straight up lying despite the wealth of evidence otherwise.
