Thanks for all the advice guys, and sorry for the delay.
I'd say that although the sisters of averlorn are awesome looking, they don't have the heavier armoured look of the darkshards as JAMOB said.
I've ordered a tonne of backpacks and a tonne of heads, just scouring the web for bolters.
Dark Eldar are overwhelmingly the popular choice for this, but I'm happier with the darkshards having what actually looks like power armour.
"Her eyes they shone like diamonds, I called her the Queen of the Land. And her hair it hung over her shoulder, tied up in a black velvet band.