I am putting a lot of efforts into the Leng Plateau, trying to make it look good. I still have 20% of the level's map to create, and I will be able to focus on the sound effects. It will be a watery level, with a waterfall and running water, so I will do the best I can to find the sounds I need ! After the Leng Plateau, I will work on R'lyeh again.
Those other worlds give me a lot of work, because I have to read Lovecraft short stories again to find more informations about them, and I cannot do everything he describes.
For the Leng Plateau, I really couldn't find any description, so I had to come out with my own ideas, that would still seem realisitic considering the elements of background that Lovecraft gave.
I'm doing the best I can !