Zack Snyder, director of the upcoming Batman v Superman: Dawn of Justice, tweeted the image of Israeli actress Gal Gadot in costume ahead of an appearance at the San Diego event.
The film-maker had earlier posted a new photo of Ben Affleck in the Batman cowl he will wear in the 2016 release.
Thousands of fans attended the annual celebration of comic books and fantasy.
They were treated to a string of film and television teasers, among them new trailers for the upcoming Mad Max and Hunger Games films.
Attendees were also shown footage from an eagerly awaited episode of Family Guy in which the animated Griffin family travel to Springfield and meet The Simpsons.
A host of celebrities were on hand to preview their wares, among them Sherlock actor Benedict Cumberbatch and Pulp Fiction director Quentin Tarantino.
The latter used a panel appearance on Sunday to confirm he was pressing ahead with The Hateful Eight, the western project whose script was widely circulated earlier this year without his approval.
Harry Potter star Daniel Radcliffe was also in attendance to promote Horns, a dark fantasy about a young man who begins to grow a pair of horns.
While there, the 25-year-old revealed he had used a Spider-Man mask and costume in order to walk around the massive convention incognito.
The first image of Wonder Woman was shown at a panel event on Saturday which saw Affleck share the stage with Superman actor Henry Cavill.
Gadot's costume drew a mixed response, with celebrity blogger Perez Hilton among those to compare her leather tunic and boots to those sported by Lucy Lawless in TV show Xena: Warrior Princess.
Footage released from Mad Max: Fury Road shows Britain's Tom Hardy and a shaven-headed Charlize Theron inhabiting the dusty post-apocalyptic world seen in the original Mel Gibson-led trilogy.
The trailer for The Hunger Games: Mockingjay Part 1, meanwhile, includes scenes with the late Philip Seymour Hoffman, who was shooting his contribution to the series at the time of his death in February.
The first picture of the new Wonder Woman has been unveiled to coincide with this year's Comic-Con.