Codex cover and Raiders of Commorragh painting guide revealed,from Germany:
[url]http://waaaghgaming.de/sieht-aus-wie-das-cover-des-dark-eldar-codex/[/url]
[url]http://descansodelescriba.blogspot.com/2014/09/ultimahoraportada-del-code-eldar-oscuros.html[/url]

I think Swanland is the artist of the cover