Ok we all know it's a simple thing to register categories to attachments.
I found the wos-media-categories plugin to be a near slam dunk, but somebody save me here... I can't for the life of me get bulk edit rockin' in the media library (upload.php) like on the posts page (edit.php)
Sheesh... If somebody has the answer that doesn't include a long dirty plugin (shoot even if it is), I would love to buy you a beer.