While we still have a long, long, long time to wait until the first of four Avatar sequels is released, the folks behind the films have been keeping a steady stream of teases going on social media. A number of behind-the-scenes images have been released on Twitter by either the official Avatar account or that of producer Jon Landau, offering up fresh looks at cast members on the virtual sets or of some of the production design – all while keeping a tight lid on what, exactly, is going on. That kind of changes today, as a new behind-…