Actually, if you look on the CAF home page, there's also the IX Exchange, which is for imaginative realism artwork . . . which pretty much covers non comic-book art such as paperback covers, MTG painted art, illustrations, science-fiction pulp art, movie poster paintings and the like under CAF's umbrella.
I think it's fair to say that not everyone who collects OA confines their interests to just comic-book stuff.
I for one, welcome the non-comic-book art diversity which I very much enjoy looking at (with the exception of fan-boy stuff or badly drawn nudie art).