That would be very useful but is beyond the capacity of this program.
Any "display" program needs to render the 3D models of locomotives and rolling stock, preferably on a piece of track and with a background
AFAIK, there is no other way in Railwords than using the Quick Drive => Create New function (where you can rotate the bare model) and take a screenshot or to pose each model in a Free Roam scenario of your choice and to take a screenshot. Since not all locomotives come with Quick Drive, and the Create New preview often has child objects in funny places.
Edwin "Kanawha" The Chessie, the train that never was ... (6000 hp Baldwin-Westinghouse steam turbine electric)
Yes, if you go to www.agenetools.com/downloads.html you will see the file Thumbnails.7z which contains about 8000 thumbnails of rolling stock, but this was compiled some years ago and does not include any recent releases.