The only way I know how o o this would be by using a sciprt and the cript debugging window to be able to see the whole extension. The folder that your DP is stored in is with a number of other files to. If you put the following code into a script, after initiating it your DP's file path will appear in the script debugging window. You will have to make sure you have script debugging turned on and the window open (plus! > Show script debugging - this is found at the top of the contact list window).
code:
function OnEvent_Initialize(MessengerStart)
{
Debug.Trace(Messenger.MyDisplayPicture)
}
I hope this is what you were after.
EDIT: This only gives your current DP