You need to apply a texture matrix to the ground model to scale the texture coordinates up. Here is some sample code:
Code:
#Number of times to repeat texture horizontally/vertically
NUMBER_OF_REPEATS = 10
leaves = viz.add('fall-leaves.jpg',wrap=viz.REPEAT)
ground = viz.add('tut_ground.wrl')
ground.setPosition(0,0,0)
ground.collidePlane()
ground.texture(leaves)
#Apply a texture matrix that scales to number of repeats
ground.texmat( viz.Matrix.scale(NUMBER_OF_REPEATS,NUMBER_OF_REPEATS,1) )