The Star Spawn are generally the size of Cthulhu himself.
Actually, no they aren't... The Cthulhi(or Star Spawn of Cthulhu) look like Cthulhu, only smaller. They supposedly built R'lyeh and are mentioned as at one point waging war against the Elder Things in
At the Mountains of Madness.
http://en.wikipedia.org/wiki/Cthulhu#Star-spawn_of_Cthulhu
But yeah, I guess the squid-faced Deep Ones are some sort of non-canon abomination then.