Honestly, when I started one, I used this guy as a base:
http://www.games-workshop.com/gws/catalog/productDetail.jsp?catId=cat440108a&prodId=prod1050011 I cut off the chain end, and added a plasma pistol, and you could also adjust the axe to be a chain axe (probably should, I just haven't done it yet to mine). Having the chain around his arm still is okay though, as Kharne does have chains and stuff hanging off of him. You'd also want to do a green-stuff fixing of his mask, to make him look like he has a breather on, as Kharne does. But it does make for an awesome start, and standing on a pile of skulls never hurts either.