How NOT to delete original account picture when uploading a new one? When a user updates his account picture (default "picture" field,) his existing picture is deleted and replaced with the new uploaded picture. This is normally done by default.

How, using Rules (or any other way,) do I prevent the system from deleting the original stored picture so that the old and new picture reside in the same directory?

Thanks. :)

Update: Someone suggested making the field multiple value. I do not want users to be able to upload several account pictures. All I want is that a newly uploaded picture will indeed replace the old one but the old picture not to be deleted. Like I said in a comment below, the Heartbeat module takes a snapshot of the account picture. When users uploads a new picture, the old picture in the snapshot no longer displays (of course, it was deleted!) and a blank empty space is shown instead. Keeping the old picture would solve this issue.
When a user adds a new pictures make a copy of this pictures with rules to a user specific directory. When a user wants to restore his picture browse this directory, let the user decide which picture he wants and copy it back with rules.