link
I call this one more than a bit fringe, and note how it tags with common media presentations:
Nordics— Eldar, Wraith, Asgardians (Marvel), Vulcans, "Angel" aliens, Ancients (Stargate).
Mantid— Alien Xenomorph, Quartermass, MIB, The First Men in the Moon (HG Wells), Starship Troopers (Heinlein), etc., etc..
Reptilian— Gorn (Star Trek), V, Unas (Stargate), Jem'hadar, Cardassians (sorta), Hirogen (Star Trek: Voy), etc., etc.,
And the "Grays"— Asgard (Stargate), or any show based on UFO abduction claims.
But, hey, now you have a "historical" basis for your tabletop aliens vs aliens vs humans gaming! 