Ahh yes, more followers of the Great Devourer. These look good! Again like others have suggested, a little wash of Badab Black can really make the model pop 3d like. Also you would be surprised at how a simple basing job can really make the models stand out. Elmer's glue, and some fine gravel, then paint the gravel black and paint it any color you like! A little green flock here and there to make it seem like a rural country side and presto you've got a flocked base.
You can find some really great deals for clock and the fine gravel at your local hobby store, or even at some arts and craft stores. I found some GREAT flock and basing material at my local train store, so that might be a place to check things out at.
How many points have you collected so far for your Nid army? You should ask Mord to show you his pocket genestealers. The damn things are so small that a small rock on the table would give them cover, and the worst part is they are 40k legal.......
Adeptus Astartes Commandments
1. Thou shalt not replace the Librarian's staff with a magic wand.
2. Though shalt not refer to thine brethren, whom the Emperor has dictated be armed with an incendiary weapon, as a "Flamer" constantly. For this has been proven to lower morale and cause strife within His Most Holy showering facilities.
3. Thou shalt not follow a Librarian around thinking, "Can you hear me now", repetitively in an attempt to drive him insane.