ok, Fulgrim and the picture. is a direct link to [URL="http://en.wikipedia.org/wiki/The_Picture_of_Dorian_Gray"]Dorian Gray[/URL]
the final resting place of the picture is never revealed, or not that i have found. though it is mentioned that fulgrim is in his mind still. he just has no controland can only observe the actions of the demon, in anguish.
as for ferrus, i assumed the itching on his neck and the black sand were indeed a vision of the match up with fulgrim. the dreamscape in the cave i thought was the fall of the primarchs and the legions, as the eldar saw them, but using ferrus' mind as the key. i found feat of iron quite a hard read, i just could not conentrate on it, TBH the audio book was the life saver for me as i gave up on the book.
i hope you enjoy the lion as much as i did
it is the best story in the collection IMHO and opens up some cool interpretations of long standing fluff.