I'm not sure the eligibility guidelines really speak to music videos since theatrical and DVD releases are the limiting factors and they don't apply, with that said I don't see why a music video should be ineligible. Maybe we need a new guideline about YouTube debut (that's how people access music videos now, right?). Of course, without a short film category, you're going to have a tough time getting it nominated, but still, you should be able to do so if it's your want.