Not enough train icons

There's currently only 3 different icons, and one would need to be for the default sounds. Luckily, we can easily add more using `TrackIconType`'s register function.

The default icons (traditional, electric, modern):

![Image](https://github.com/user-attachments/assets/2bc6a6a9-4b33-492b-a0a9-fdc6a50979f5)
