A few years back I attended a workshop by one of the artists who worked on an incarnation of the John Carter movie prior to the Disney version. I got to see a pitch reel of what Kerry Conran (director of Sky Captain and the World of Tomorrow) had planned for his adaptation of Edgar Rice Burrough‘s classic science fiction story Princess of Mars for Paramount.
That version was never made, and what we ended up with was Disney’s John Carter, starring Taylor Kitsch which became a box office disaster and generated an inordinate amount of hate for what was an alright, if a bit mediocre movie.
Harry Knowles (of Aintitcool.com) was set to produce Conran's adaptation, and he has recently released a high-res version of the pitch reel, it is filled with some fantastic concept art and some interesting CG tests. A low-res version of this video has been around the internet for a while, however this version is sharp and gives a good idea of what Conran's vision for the movie was.
It doesn't tell much in the way of story, and you might get a little lost unless you've read Princess of Mars, and some of the other Barsoom books. What it does give is a great feel for the world and characters, which in my opinion is much more important. It's a pretty great dive into the world of John Carter, enjoy: