There's one alien form left to concept, which is the Shrike. Khaoz, who did most if not all of our alien concepts, made one for the Shrike, too, but while the appearance was very good it didn't fit our requirements for gameplay and would have been a risk in terms of animation when moving on the ground. Khaoz had a different gameplay in mind when doing the concept and didn't see a way to transform it into what we asked for. We made the arrangement of passing the shrike on to another artist, which could be you if you're interested.
The Shrike is a flying alien. The gameplay mechanics are currently being implemented by Ishq and are outlined here. You can have a look at earlier concepts. Khaoz' second take on it had the issue of lacking feet which are needed to push the Shrike into the air and give it limited walking abilities.
The requirements from a gameplay perspective would be:
Has roughly a square footprint. When flying, the wings may reach slightly out of it and when on the ground, there may be free space at the sides.
Has claws or some other melee weapon at the front that are used to hit the heads of humans when flying over them. It's not necessary that they can be used to attack when on the ground, but it wouldn't hurt. (Most of our alien forms have six limbs and the first row is used for both walking and attacks.)
Has feet to jump into the air. On the ground it walks slowly, roughly at the sped of the Granger. The Shrike should only be strong in the air but it should be able to walk through ventilation shafts, have a rest in the base and potentially walk on walls.
As all our alien classes, it should have six eyes and an appearance somewhere between insect and reptile.
If you have any questions regarding the flight mechancis, talk to Ishq on IRC or ask here.