Ghostcrawler's responsibilities are essentially class balance, feature management (LFD/LFR, transmog, etc,) itemization/stats, UI, and that the world is functional.
Ghostcrawler doesn't say what races the art team and the game director (Chilton) and creative development (Metzen) decide they want to add. Ghostcrawler simply makes sure everything is playable and for his team to try to balance it.