„Key Visuals“ — which are usually referred to as „key art“ in the US, are high-resolution promotional „poster images“ that are used to market the show. Key art is very high quality, as it’s intended to be printed on anything from DVD boxes to posters. When it comes to anime, it’s usually delivered as a massive, massive Photoshop file, complete with a background, and often, every character on a separate layer so that they can be rearranged depending on what the art is being used for.

Quelle: What Is „Key Art“ And Why Is It Important? – Answerman – Anime News Network