Taking into account the reference attached in the brief, I thought that a hand holding the king's crown instead of the character, and passing it to the head would be the best way to represent the concept art well. In this way I managed to create a board scene with the character inserted in it at the bottom of the poster and thus project the shadow of the chess piece.
The poster style is fully hand-drawn with the phrase "an original documentary" above the title to give more authority to the advertising piece.