Maximus, after known as Maximus the Mad, is one of the members of the Inhuman Royal Family who could feasibly work on the show. He's Black Bolt's younger brother, and often tries to usurp the King and claim Attilan for himself (which has has succeeded in doing in one comic run). He has genius level intellect, especially as an inventor, and also has the ability to control the minds of others, although his slight insanity can often hinder these powers. As opposed to a character like Black Bolt, who probably needs to be done properly with a big budget behind him, Maximus could work on the show, and would serve as an introduction to the world that'll be explored in the film. He'd make for an excellent foe for S.H.I.E.L.D. and the Secret Warriors, which would mean he'd not only help in causing excitement for the movie, but be great for the plot of the show as well, and the development of the powers of other Inhumans going up against him, most obviously Skye.