John Luetke

Allows you to change the author of a piece of media by adding a drop-down list of all your blog’s users to the “Edit Attachment” screen in the Media Library.

Media Author

Allows you to change the author of a piece of media

Ruslan Mikhno

This is a very simple plugin that allows you to bulk change author for media files.
The action is added in the “List” view of the Media Library.

Bulk Change Media Author

Bulk change author for multiple media files, using the default WP Media Library.

Media Author vs Bulk Change Media Author