Every swarm of villainous monsters needs a leader. They need a creature of such terror and monstrosity that they nameless rank and file pale in comparison to the sheer horrific might of the army's centerpiece. This is it.
Mathhammer and I talk about this in the comments of the previous posts, but I am adding a fourth 'ball' of snow to the Stormlord's torso. It's just going to serve to make him as tall as he needs to be (ironically, I am trying to stay WYSIWYG with model size), while keeping the size of the individual ball reasonable. See, in order to make a three ball snowman that tall, each ball would be much larger in volume. Also, I like the way it looks. It continues the 'four' theme I have going here with the Ice Sabers and eyes.
I was originally planning on using Tyranid Primes for my HQ selection, and I may still, in low point games, but I think I like the idea of a massive snow beast as a centerpiece for my army. What do you all think?