That picture is by Duo Cartoonist, the same people who did the fantastic "The Moon Rises" animation! It was for an animated fan-origin story about Luna and Celestia called "Choices", which was unfortunately cancelled (iirc, Duo wanted to start focusing more on original works rather than fanart)
Not gonna lie, that was the first thing I thought of when I heard "Don Bluth-inspired mlp"
would've loved to see the finished project.