As soon as the first leaked art revealed Hawkeye's new field outfit with Ant-Man riding his shoulder we know the iconic scene from Marvel Comics where Ant-Man rides an arrow fired by the archer would be a must for the MCU. And it's true.
As for Sharon Carter a.k.a. Agent 13's appearance on Team Cap in the art, that's important for two reasons. Firstly, she's going to be the love interested of Steve Rogers in the film and second, she's stepping up as a female lead in the field in the wake of Evangeline Lilly's absence, who was originally planned to appear in the movie as Wasp but scheduled out due to her pregnancy.
Sorry, no Spider-Man anywhere. If Disney and Marvel play it smart, Tom Holland's Peter Parker won't appear in any of the pre-release marketing materials, a la Luke Skywalker's absence in Star Wars: The Force Awakens promos and merchandise.