Check out my space train kitbash to be used on my HO scale sci-fi model railroad “The Mines of Xenon”. That’s a Bachmann E60 chopped up to fit an Atlas SD45 with the guidance and encouragment of renown space modeller Jack Hess.
You can find build informaiton and progress on the loco and layout on my blog.
For steam engines, it would be interesting to see someone’s interpretation of them from Brandon Sanderson’s Mistborn series (not the original trilogy, the newer ones have advanced to steam power and other such things).
Hollywood special effects people have been known to ‘kitbash’ things like that. The original Milennium Falcon model used in filming Star Wars includes the front section from a B-29 bomber kit.
Speaking of which, the upcoming movie, “Solo: A Star Wars Story” has an actual “prototype” science fiction locomotive in the film, according to the movie’s trailer: