thank you for the suggestions. Pak128.Britain does not currently have any narrow gauge infrastructure: vehicles, depots, tracks, stations, bridges, tunnels or crossings. I think that narrow gauge is on the to-do list somewhere, but it's fairly low down. Do you have any interest in doing the graphics (which is easier than it looks at first)?
One thing to note is that a great many of the more recent vehicles on your list (especially the 21st century built steam locomotives) are only commercially viable in reality because of the use of the narrow gauge railway on which they run as a tourist attraction. That aspect of economics is not simulated in Simutrans, so we have to make sure that only vehicles that are viable for use on a purely functional transport system are included.