Adding Custom Images to Old Posts

Is it possible, or could it be possible in the future, to allocate custom images by Author, which cover all of their old posts too?

We have over 23K posts and a lot of old ones get posted on Facebook and Twitter – but without the Author’s image.

I would like to be able to allocate a Custom Image, a Custom Twitter Image and a Featured Image for each Author by default.

FYI, currently for new posts, I paste in the URLs for the Custom Images and Custom Twitter Images, rather than select them from the library.

Regards and thanks,
Angus