Look at like 90% of champions and you will see riot copied, or how they would put it "inspired" by other video games, movies, and tv shows to make their champion concepts.
There's some influence from alien, yeah, but the Void and its inhabitants are much more heavily influenced by HP Lovecraft.
I wouldn't be surprised if Alien, or the artist who designed the Aliens (H. R. Giger) was an influence to a lot of the designers and artist working at Riot Games. It definitely could be a homage to either, or both.
Alien is an influence from the general concept of those type things in the past. Cho is from a person of the same era.
Riot was probably influenced by Blizzard (Starcraft) which in turn was influenced by Games Workshop (Warhammer 40K) which in turn was influenced by Giger.
All are copying moray eels in any case.
the new splash art for Cho reminds me very much of Violator from Spawn.
in game not so much. too fat :D