I think it could be in degrees. Truly relevant content should be:
Japan, anime, manga or japanese games, culture and music, and japanese artists as the core topics.
Not completely on topic but fine on other grounds:
art inspired by japanese artists, anime influenced in style, or high quality fantasy, science fiction or technically good illustration.
Not on topic at all and completely out of place:
IRL Porn photos, real life landscape photos and portrait photos of no relevance to any topic on this site, western style political cartoons with no basis in classical anatomy or japanese styled form, or any cartoon that appears in an american newspaper, comics with neither any basis in japan while ALSO being poorly drawn.
A distinction could be made for superhero comics as many japanese artists make illustrations of that, and many western artist uploads with that sort of content are well done. This should be made clear for games too, and science fiction and fantasy, if well drawn, does fit into the archives neatly. Things like american cartoons though, with no "east meets west" or anime styling or relation to japan in any way, doesn't fit. This would keep out Cartoon Network/Nickelodeon cartoon art from being slipped in, since much of that doesn't have value from a higher level art standpoint. It should also be noted that extremely cartoonish art should be judged with more scrutiny, including chibi, or pictures of japanese copyrights done in western cartoon styles and forms of design, regardless of cultural source.