I don't know if this will answer your question about sources, but maybe doing what I do with media might help. Whenever I work on a person I click on their media tab in the right pane. I then click on each item to hi-lite it and right mouse click to get the drop-down menu and choose "rename". I then name it using my preference, Year - LastName FirstName DocumentName OtherInformation.
I try to rename media as I'm merging it into my FTM tree; if you scroll down in the merge window it will as you if you want to rename the image. Just wish I had come up with this years ago when I first started, I have a ton of media that I need to rename.