This snippet randomizes the z value of all vertices by a given amount. (be in object mode, with a mesh object selected)
import bpy
import random
verts = bpy.context.active_object.data.vertices
for i in verts:
i.co.z *= random.uniform(0.7, 1.3)
In combination with the separation script from a previous post you can get some neat effects, maybe this will plant some seeds
