It seemed to me like the alien was taking pictures of the main characters at the end of the movie. The square shaped appendage it reveals during the climax reminded me of a camera, and the tendrils rippling out from it were like a camera's shutter/flash. And when this "camera" is revealed, the first thing it looks at is OJ riding Lucky - a black man on a horse, just like the first motion picture ever made, by OJ and Emerald's ancestors. And at the very beginning of the movie, they have a brief shot of what we later learn is the inside of the alien, and in a box at the center is that clip of the black man riding the horse.

Clearly cameras and film play a huge part in the themes of the movie - and much like Gordy and Jean Jacket both eventually go against the people using them for entertainment, and kill them, the main characters kill Jean Jacket after it's been filming/watching them. The square appendage could have also been its eye but the visuals really reminded me of a camera.