RLyon,
You would need to setup a server that the 6900 phone can perform a lookup of the extension number; the pictures should be .png and the size should be 150x150 pixels. So for example of the extension number is 1000 then it will look for 1000.png from the server.
Look in the 6800/6900 SIP Administrator manual as you have to setup the configuration files to support Avatars. I believe it is on page 5-45 of the latest manual; listed as Picture ID Feature.
Thanks,
TE
