Edit : V2 , I've updated the model with two much cleaner versions for Genestealers and Termagants. I hope this helps!
For the Termagant model, the keywords are: k1nkR4nid, alien, monster, and chitin for the base. You can add tail and claws if you're having trouble making them.
For the Genestealer model, the keywords are: g4nel0v3r, alien, and monster for the base. You can add four arms and claws if you're having trouble making them. As a bonus, to make a Broodlord, add alpha and big brain.
V1 :This is my first model because there weren't enough Tyranids available to my liking. Probably won't work, but in a misunderstanding it might work. eddit : It seems to be working, and not too badly either ! Don't hesitate to post your images; I'm curious to see what you can create :)
Description
First sketch; the keywords seem to be Tyranid and alien. Use "huge Tyranid" if you want something like a Tyrant, or "small Tyranid" for a Termagant.