To create mountains in the editor of Bryce is a true art, it is not as easy as it seems. 
A very simple clue: 
In Bryce you find dozens of ready mountains for use, therefore: 

• Choice one of your pleasure and later alter your characteristics (size, height, width) 
• Use some brushes to retouch 
• Use two or more mountains inserted with different sizes 
• When using a texture or material, modify your properties 
• Try to use more than a material / texture 
• Depending on the atmospheric composition some lights will help 
• Remember that the final result can suffer influence of the characteristics of the used atmosphere 
• A lot of times a good texture is bad with a certain sky. 
• I usually use the same texture of the land and later I modify for the mountain 
• A good imagination dose is a very important ingredient 
   
  I hope has helped. 
  Hugs.