Hi, VampyreBe..

I'm not sure if the following applies to V5E (I have V5I), but:

To get your mountain taller you could try stretching it vertically in the side or front view. (Select the terrain then drag upwards on the little square in the middle of the top of the bounding box).

To make multiple mixed textures:
Use the Advanced editor.
Double-click on one of the 2 textures making up the existing texture. This should bring up the underlying simple texture for that part. Make that mixed.....

Cheers,
Diolma