Yeah, original owner is what matters unless the other person adds something of significance like a commentary or another video, which is a whole new can of worms.
Here is how you would cite:
APA
Norton, R. (2006, November 4). How to train a cat to operate a light switch [Video file]. Video posted to
http://www.youtube.com/watch?v=Vja83KLQXZs
MLA
Shimabukuro, Jake. "Ukulele weeps by Jake Shimabukuro." 04 April 2008. Online video clip. YouTube. Accessed on 22 April 2006.
http://www.youtube.com/watch?v=puSkP3uym5k
As for pictures, you would include information from both the original artist and where you got it from.