As far as I am aware, the art show has always accepted different genres of art. The ones listed in the rules are sci-fi, fantasy, and anime. At no time have we excluded a genre that did not apply. I think that the art show has morphed into a place for artists to show their work no matter the purpose of the convention.
If you look at the convention itself, not all activities relate to anime - there were panels on internet memes and webcomics and fiction. We have live gaming and rock band tournaments.
I guess the bottom line is that I would rather have a variation of art that may or may not be anime related and have a full show instead of limiting it to only certain genres and seeing blank spaces where art might have been.
Since this was brought to my attention I will go ahead and revise the art show rules so that there is no limit to what will be accepted except for content itself - whether or not a piece is appropriate to be viewed in a pg-13 art show.