(not sure if this will work)
go to this link below and download the plugin 'Load image from URL at runtime'
Then use the facebook plugin to get the user ID..
Then call this link graph.facebook.com/19292868552:
Replacing the id at the end,
once you have this data, you have access to there profile picture,
for this example -- profile.ak.fbcdn.net/hprofile-ak-ash2/276791_19292868552_1958181823_s.jpg%22
So you would need to figure out how to get this link once the data is received from the first link..
Sorry if this was of no use to you, Im not sure of any other way to get it....