This painting was for the Lovecraft film festival, so the only real requirement was that it had some connection with film or theater. It's sort of a joke, but the idea that it is some form of extreme documentary-making. My thoughts were that they might just be recording her, but I like your idea that they are trying to glean some wisdom via conversation. I actually painted the crew and shub-niggurath separately and photoshopped them together, so there are two versions (with and without crew).
Hmm, I'm not sure he defined it, and I would suspect there'd be many languages if we were to consider all the various races. So many subsequent writers and game designers have expanded on HPL's universe, I am sure someone's explored the idea of languages if Lovecraft hadn't. I wonder if the larger entities such as Shub-Niggurath and Cthulhu communicated in a telepathic manner? I have heard of Aklo referring to a form of magic, though it could have it's own connected language, too.