There is a helper function that prints some info to terrain tiles, that can be used for example to debug problems with terrain rendering by identifying the infringing tiles. Here's how it looks:
The text is printed over the generated terrain textures. For more detailed tiles a different approach has to be used - text is written as a different terrain material. It can look like this when writing with stone:
Of course not only the material type can be modified, but also other its parameters.
It can get pretty cryptic up close:
Not sure what this could be used for, aside from debugging help and some labels on roads .. maybe it will inspire someone
