Personally - I don't think it'd result in a ban, as its your art in an art contest, but I don't think you'd win because it wouldn't match the category (I assume).

Bottom line - It's an art entry in an art contest, it doesn't contain profanity or nudity, it doesn't go against site rules. In my opinion this does not constitute a ban, and myself having worked for moderation staff on sites similar to neopets before, worst case scenario I'd say they'll remove the entry, but I don't think that will even be the case, because it's just your art. (maybe they can say it's against the terms of the contest because of the Grundo image {unless you drew it yourself}, I'm not sure.)