Great job! Like your depiction. Fits with Lovecraft's description pretty well while having good original elements. One thing though. Island of R'Lyeh is ment to be many fathoms deep under the ocean. When the stars are right the island will rise and Cthulhu will awaken from his eternal dream. Another thing is that Cthulhu is associated with water. So land foliage doesn't look right here. It would have been better if those plans were some algae and polyps or something completely alien altogether.