First off, I do like the main colour choices. That grey/blue/green really gives them a heartless feel. There are three things that could be improved on; the teeth, the eyes and the yellow on the weapons. The teeth are too white, far too white - paint them like you would paint horn, and they'd fit right in. They eyes are just a bit dull and flat. A highlight would make them far more alive. The worst offender IMHO is the yellow. I'd not have used the yellow like that, since it detracts from the rest of the miniature, indeed the entire squad. It really draws the eye away from everything else and also leaves one wondering why the venom cannon has no yellow on it. And after having done that, there is very little variation in it, it looks like flat yellow to me. An orange wash and some highlights with a yellow/white mix would do well. Ah, one more thing: clean up around the edges of the bases, intentional or not, it looks like the glue overran the edge and you didn't wipe it off. I like the 'nids and for the most part, you've done a nice job on them.