works Rated 4 out of 5 stars
Does not always work, then shows only gravatars, but not the photos from address book.
Posted a list of my addons here http://www.thunderbird-mail.de/forum/viewtopic.php?f=39&t=44680&p=233268#p233268
Any restrictions for picture format, size etc.?
[EDIT] Does not choose the right (main) address book, if same addresses are in more than one address book.