I suspect the Cultist theme in Rogue Stars was meant for something a bit more Grimdark, but I like it for seriously weird alien types.
Built using the old "Large Sadistic Demons" from Asgard, currently in production as "Flesharons" through Alternative Armies. I love these nostalgic old models, simple as they are.
As far as Rogue Stars stats go, I'd use the following:
Tactical Discipline: Gestalt
3 x Servicer Xenopods (the little guys) each with the Vegetable and Psionic traits and the psionic abilities of Blink, Healing, Levitation, and Telekinetic Push (30XP each)
2 x Enactor Xenopods (the mid-sized ones) each with Vegetable, Psionic, and Psionic Mastery level 1, and the psionic abilities of Blink, Levitation, and either Nightmares or Telekinetic Strangle (30XP each)
1 x Director Xenopod (the big critter) with Vegetable, Psionic, and Psionic Mastery level 3, and the psionic abilities of Blink, Mindscream, Nightmares or Telekinetic Strangle, and Teleportation (50XP)
No equipment at all, relying on their mix of psionic abilities for offense, defense, and mobility. They get a huge +6 to psi rolls initially due to Gestalt, but if you can inflict casualties on them they fall apart pretty quick. Early priorities for spending XP would be levels in Psionic Mastery, followed by more psi abilities and eventually defensive and buffing traits. They really don't want to melee anyone (which is, again, probably not what the designers were thinking of with the theme) and focus instead on using psi abilities to move themselves and their enemies around, heal damage, accomplish goals (or foil the other guy's) and generally be irritating. The Director's ability to teleport (at +9 to the die roll!) and then pop a Mindscream is the biggest offensive trick, and the Servicers' TK push lets them make juicy clumps of targets for to aim for with it. Robots are a problem for the crew as a whole, although TK strangle (aka "mentally unplugging your CPU, tin man") gives you something to use besides unarmed combat.
The species aren't really Vegetables, but the trait seems like the best way to represent their extremely alien nature. Bit of extra durability, immunity to some effects, resistance to others, but (as with all horrific infestations) they don't like being purged with flame.
The other "Flesharons" make a very different crew, this time relying on integrated cybernetics. Some background fluff, the "Awfuls" (as humanity has nicknamed this largely incomprehensible species) are undergoing a schism. The Purists in the first post are the Old School faction, using psionics for virtually everything. These guys are the Melded, a recently arisen group that eschews native psi power for biomechanical cyborg enhancements.
Suggested game stats:
Tactical Discipline: Hard to Kill
2 x Sickle Drones (the little guys) each with the Ambidexterity, Claws, Tough level 1, and Vegetable traits and two Bionic Arms (30XP each)
2 x Warmasters (the big guys) each with Ambidexterity, Big, Claws, Tough level 3, and Vegetable traits, with two Bionic Arms, Cyborg Body, and two Torso Weapon Mounts (laser rifle and sonic rifle) (70XP)
Extremely tough for critters with no actual gear, with even the little guys getting a +4 on most damage result rolls against them and the big guys going to at least +7 (more if a hit lands on a bionic arm). Hard To Kill makes it hard to make early wounds stick on them as well. They're usually going to be outnumbered, but having Ambidexterity on everyone lets them get more attacks per action than you'd expect. Not very accurate attacks, but lots of them and with some fairly nasty weapons. Don't forget all their Claws have Crunch due to the twin Bionic Arms, so you can remove troublesome enemy equipment if need be.
This was originally posted last year over on Lead Adventure Forum, but I'm mirroring it here since my original photo links have died.