I think it's worth tagging them with their name. When describing a picture with tags i would consider it important to know who the person (or animal, whatever) on the picture is, even if it has just 1 post in the end. It's just my opinion on this, but like this the tagging is more accurate.
And for the sourcing, i didn't know that you planned to do that later. If it is such a big problem, i can still remove those, or exchange them with the sources you have.
People assume that if there is only one picture of it now, it will remain that way forever. We only have one Ponyta Moemon now, but people could make more. Having a tag for the sake of possibility is a good thing.