You can extract them directly from Messenger's own msgres.dll file using something like
Resource Tuner (free 30 day trial version) or
Resource Hacker (free). They are stored as PNGs in a filmstrip.
In WLM 8.5 Beta, they are in the "4000" resource. 202 is a png with the static ones and one frame from each of the animated ones, and 257 to 267 contain the animated ones individually. Not sure about other versions, but they should be pretty easy to find.
Hope this helps