Mogging wasn't a doubt (for me at least) Op asked for the artefact appearence, meaning the various skins proper of the artifact and not form other weaps.
As far as I know, not being in the Alpha party, they are different things.
The question is if they behave in the same way. If yes, Great! It means you can mog AND reskin your weapon separately. If no, Laaame, because yes you can mog differen skins, but not different artefact appearences.
From the Official site, the Shaman's art preview clearly shows that he's wielding the molten and the original appearence of doomhammer (source
http://eu.battle.net/wow/it/blog/19941529/ )
However, when it comes to Warriors and DKs, in the preview they're wielding the same appearence.
So is not clear, but there is hope.