I'm sorry for not being clear, but I meant to put the emphasis on using the "correct" file name in the /OVERRIDE directory. (I was being too polite to say you might not have been doing that.) It always works for me.
However, now that I think about it, I remember a couple of mods that use their own special directories instead of putting files in the /OVERRIDE folder. For example, I think the Kelsey mod stores the files for Kelsey's spells in a special folder. Perhaps the Xan mod does the same thing. Why don't you look in directory from which the Xan mod was installed and see if his portrait is stored there. If you find it, maybe all you have to do is replace it with the portrait you want. (Make sure the file name is spelled correctly, hehe.)
