Sam, I have Roger Carp's book on dealer display layouts, I'm trying to figure out how I can help. I'm sure the forum would frown on wholesale posting of the book's pages for copyright reasons, but "fair use" provisions allow reproducing a small number of pages if we can narrow it down.
The first part of the book is mostly text, a general historical narrative.
The second part of the book has color pictures of some of the surviving displays, one is standard gauge but it is just a simple oval, the attraction of the display comes from other elements.
The third part is about construction techniques for building your own, which seem to be generic enough information that could be obtained elsewhere.
Part four is the main part of the book, and consists of B&W photographs, track plans, and wiring diagrams for many display layouts. Also materials/component lists for each display layout. There are close to 50 pages of this. The information on each display is a 2-page spread. As far as I can see, they are all O Gauge.
Not sure how to narrow these down. The displays are numbered (D-133, D-190, D225, etc.). If you had enough information from other sources to know which display you were interested in, I could either post or email you the pages on that layout.
I know that in past threads, some forum members are familiar with some of the D- numbered layouts and have favorite ones to recommend.
David