This is now officially in KDE 3.4. The files are here only for historical reasons.
This patch adds support for X-Face headers to KMail and KNode. It is based on the compface library, originally written by James Ashton.
In KMail, X-Faces can be set per identity. A X-Face can be either entered directly, created from an image file or created from the image stored in the KDE addressbook in the user's contact. KNode does display X-Faces only. You have to set them using a custom X-Header.
You might need a valid X-Face string. Get one at ace's X-Face page or use the Online X-Face Converter to roll your own. The patch is for KDE 3.3.
Just apply the patch in the kdepim root directory. Recompile. Enjoy.