For this process I depend a lot on searches using google images, pintrest and art sites like polycount or art station. In addition to this, going out there and taking photographs myself is a huge tool to get reference for little details that might be harder to find online.
I save all this reference material into one folder and I then assemble it into a single reference sheet. This allows me to cull through the images and start to clump together similar concepts. The reference sheet becomes incredibly useful once I start modeling, and I can just keep this once sheet open with all my reference in one place. The final jpeg tends to be one really high resolution file I keep panning around. Sometimes the file can be as big as 9,000 x 9,000 pixels.
For this project I created two separate sheets one for the front area or the propulsion systems, and one for the cabin/carriage area in the rear. Most of my sources of inspiration for these sheets were early 20th century race cars, concepts and design from "The Order", as well as Nikola Tesla inventions and steam powered cars. My love for automobiles was definitely a big influence for this piece, I even included a Morgan three wheeler which is one of my all time favorite cars.

