In the case of multiple sources?

Here's my case:
This is the image: post #64972
I know the URL of the image on the artist's website, but there is already a source recorded on it from another website.

Should I leave the current record of the source? Replace it? Or replace it and put the last source somewhere else, maybe in a non-bump comment?

Edit: Another case, there's already a source recorded from another website, I know the URL from the artist's, but it returns a 404.

What's more important is that, seeing as you already know the artist's homepage, you add an artist entry for him/her, unless there already exists one in the database, and tag the posts with the tag for the artist.

Okay, I guess I missed that one... ^^;

If the source is an image board URL where the image was reposted, and you know the original URL on the artist's website, you should replace it.