Music doesn't really have many limits as far as AMVs go. If you consider trailers, even just talking can be considered an AMV. Or some experimental stuff that doesn't have audio or other weird things like those might pass too. Really, the requirement is pretty much just in the video. And yes, I personally think that mikumikudance would count as anime since, IIRC, it's a videogame that allows you to create dancing cutscenes with the vocaloids or something along those lines. You could just list that as video source, or original animation would be fine too, perhaps.