The MSN client allow users to handwrite text or drawing which are then displayed as still images in the conversation. I think Papyon has already support for it but we need a way in the spec to represent it. See https://bugs.freedesktop.org/show_bug.cgi?id=26481 which this one blocks.
Maybe this should be implemented using HTML text and embed images? (bug #15449)
Does the HTML spec covert the way to embed custom image and how to transfer them from the CM?
You don't actually need the HTML spec; if you receive the handwriting in an image, and put that image in a Message_Part that is not marked as an alternative for another part, then UIs are meant to show it. (I don't know of any UI that actually does this yet; MSN Handwriting will probably be the reason to do so, in practice.) See the "lolcat" example here: <http://telepathy.freedesktop.org/spec/org.freedesktop.Telepathy.Channel.Interface.Messages.html#org.freedesktop.Telepathy.Channel.Interface.Messages.Message_Part> and in particular, search for the text "A client that does not understand HTML".
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.