Figured I'd share this with you lot.
Rather than super specific army lists, what you get is a set of "archetypes". I basically went through popular scifi and looked at what general types are common, and then provided rules for those.
For each, you get battlefield and psychological traits as well as how their leaders function.
Warriors – Races with a warrior culture, possibly caste based.
Depending on outlook, these could be Orcs (40K), Klingons (Trek), Turian (Mass Effect), Aslan (Traveller) or similar.
Converted – Humanoids (humans typically) that have been absorbed into a hivemind and been "upgraded" with cybernetics. Borg (trek), Husks (Mass Effect) and the Strogg (Quake 2/4)
Swift – Small winged humanoids. They move fast and go squish. This is pretty much the Droyne from Traveller but if you figure they are running fast instead of flapping wings, it could work for other squishy, fast races.
Precursor – Old, refined aliens with slight psychic abilities. Eldar (40K), Asari (Mass Effect) or Vau (Fading Suns)
Soulless – Robotic hordes. You know what this is, without me explaining it :). Geth (Mass Effect), Terminators (the movies) and similar.
Engineers – Physically weak aliens with a knack for technology and hacking. Quarian (Mass Effect) was the main inspiration here.
Slavers – These are basically Grey's (and their derivatives like XCOM sectoids)
Feral – Strong, aggressive beast-aliens. Any number of angry, cat-people in science fiction. Also Krogan (Mass Effect)
Manipulators – Tentacle aliens that manipulate events around them, masters of intrigue. The archetype here is pretty much the Hivers from Traveller.
The Many – identical, hiveminded clone species. Inspiration was the aliens (and end-stage of humanity) in Forever War.
Horde – Mutated hordes with terror-weapons. An option for people with old zombie-types from Warzone or whatnot.
Swarm – Bugs, Xenomorphs. You know the drill.
edit: You also get a handful of alien traits to build your own or modify the ones above.