I'm not entirely sure. But part of determining a hub score is the QAP (quality assessment process) as well as the length and uniqueness of a hub. You can read more about it here: https://hubpageshelp.com/features/Learning-Center-... .
Also, you are supposed to be citing the images that you use in your hubs. And we're not supposed to use copyrighted images either. You can only use images that are in the public domain or that have the creative commons license. You can find out more here: https://hubpageshelp.com/media/Learning-Center-leg .
As for videos, I read in a forum thread here somewhere that it's okay for us to use videos on our hubs and there's no copyright issue because if we can embed the video in our hub then that means we can use it. Here's the link for that forum thread: http:// hubpages.com/forum/topic/111641#post2383519 . Hope this helped.