What program are you using to make the terrains? You need a program that has a "Greyscale" option, such as
GIMP or Photoshop. Simply using greys, blacks and whites won't work.
Make sure:
- Your map is either 513x513 or 512x512
- Only one layer
- There's no transparency
- It's saved in .png format
- Saved as NAMETerrain.png and is located in your Terrains folder, preferably the map folder
- No alpha channel
- In Greyscale
There's a GIMP tutorial
here for making heightmaps, which you may find helpful.
Hope you find this helpful, if not just let me know
