How do you make your own terrain testures? The kind that are effected by the height of the terrain. I need it for this project.. I need a snowy terrain but the ones that come with bryce don't work to well with it..

How would I go about making my own? The one used in the sample pic is just.. ew... snows fine but the 'rock' part is just.. ick.. too stripy.

Also why do my trees have a hump in them? All I did was remove the leaves on them.