Thanks to an insightful interview with Colin Cantwell by Jason DeBord of the Original Prop Blog, we now not only have some long-wanted insights into Colin Cantwell's role on Star Wars, but to everyone's astonishment, also never before seen concept art!
In fact, not just never before seen, but never even talked about! Cantwell's pieces were auctioned off in California in late 2014; hopefully these were documented and will end up in a second edition of The Making of Star Wars some time in the future.
For now, feast your eyes on a different version of Star Wars indeed.
Per request of Colin Cantwell, the reproduction of the images here have been watermarked.