Release early and release often.
The attached file is in no way official and may very well corrupt your game and cause the next world apocalypse. Use at your own discretion. Which at the moment means unzipping into the graphics folder, loading it up in SHPedit and looking at it.
I am not an artist so no whining about the quality.
I have gone with "European" sized rolling stock with one car per hex.
A "proof of concept" scenario is in the works.