Let us not forget the great unsung hero, Colin Cantwell. He was there at the beginning and helped inspire the look and feel of Star Wars. He pioneered the technique of kitbashing and was hired by George to design prototypes of the ships while he was still working on the first drafts.
The likely reason Rinzler didn’t include these in the book is that they’re not in the Lucasfilm archive. Cantwell still owns all of his original work for the film.
Here’s a great video interview series with Colin Cantwell about his work and history with the industry.
The Star Wars portion starts in Part 3. Lots of amazing stuff that you’ll find nowhere else, including artwork.
Yeah, I can definetely see how these might have been some of the pictures Rinzler was talking about
http://kitbashed.com/blog/colin-cantwells-concept-art
(EDIT: are these actual SW concept art by Cantwell?)
The “sci-fi hero standing next to a futuristic vehicle” could be a reference to a Buck Roger’s photo. In of one the videos you linked to Cantwell mentions how this vehicle (picture below) was based on a Buck Roger’s image Lucas showed him.
Kitbashed.com also suggests that this Flash Gordon comic from 1971 (image below) was an inspiration for Luke’s speeder. Although it doesn’t match the description of the attached images that Rinzler mentions, this could definitely have been an inspiration at some later point in the production.
