@finitepower
You can already add images to other people's characters, if that's what you're asking for? Scroll to the top of the screen, hit "submit new image" (in the dropdown), add a character, and then click the little arrow to the right of "My Characters". That brings up options to pick from other people's characters, search for characters, or directly input a character ID to add an image.
The person will then be notified (in transfer requests) with a request to accept the image.