Almost working with 3.0.4 Rated 4 out of 5 stars
This could be a good replacement for MessageFaces, and installed well in Thunderbird 3.0.4, but ... I pointed the local store of images at the same directory/folder as that I used for MessageFaces under TB 22.214.171.124 (& earlier). DCP found the files in there, but once it found the first (of only 4) image it doesn't remove it, or change it, when I move to a different message.
Most of my testing is on a Newsgroup that I am a member of.
The thumbnails do change against email address when posting a new message though.