Editorial from editor, tutorial from tutor, posterial from poster. The construction is natural enough that the word sounds like it ought to exist already. That makes it a good brand for anything in the poster and print business without being literally descriptive, and the coined form gives it trademark room that “posters” alone would never have. The market is healthier than people assume. Gig posters, screen printing, art prints, film one-sheets and the whole design-forward wall decoration business keep going, supported by a generation that buys art before it buys furniture.