Thankyou! Funny you should say Lovecraft. I'm contemplating doing a Cthulu monster plaque at some point (Though I've never read any of the books, but I've seen images.) Just uploaded a new Predator plaque too to kinda match my Aliens.
You might want to read the short story "The Call of Cthulhu" before you tackle the plaque. Lovecraft gives a pretty complete description of Cthulhu itself, though it's very open to interpretation. According to Lovecraft, Cthulhu is worshiped by cults all over the world; naturally, each has its one spin on the monster.
You might also find inspiration in Lovecraft's "The Shadow Over Innsmouth,""The Whisperer in the Dark" and "The Dunwich Horror." Have Fun!