The first image reflects Billy and Tharbis at the end of the dancical running triumphantly away from the Savoy Ballroom where they faced down death and won the dance contest, freeing them for a better life. It shamelessly borrows West Side Story poster imagery. And, like the immortal play, it's warring families have been replaced with warring gangs, one white, the other black.
The second picture borrows from the "Balcony Scene" but with a twist: Billy uses his dancing to express his love for Tharbis as she watches him tap dance under the streetlight outside her Harlem tenement apartment. No words, no singing (or rain), just dancing. Oh, yeah, at one point Billy reaches into the future and borrows from Gene Kelly and Singing In The Rain by jumping up on the streetlamp-- but jumps off and lands in a split in homage to the Nicholas Bros.*
Like the above-the-title copy says, this is a "Celebration of America."
*Jitterbug! doesn't require "triple threats" from any of its performers. It just needs actors who can dance really, really well. :)