Here is some sample code that uses the vizact library to create an action that does what you want.
Code:
import viz
viz.go()
#Create quad for displaying texture
quad = viz.addTexQuad(pos=(0,1.8,2))
#List of texture filenames
files = ['ball.jpg','gb_noise.jpg','brick.jpg','lake3.jpg']
#List of texture objects
textures = [ viz.addTexture(f) for f in files ]
#Create action that randomly waits between 2-6 seconds
waitTime = vizact.waittime( vizact.randfloat(2.0,6.0) )
#Create action that randomly applies texture from list above
randomTexture = vizact.texture_node( vizact.choice(textures,vizact.RANDOM) )
#Create sequence that repeats above actions indefinitely
my_action = vizact.sequence( waitTime, randomTexture, viz.FOREVER )
#Add action to quad
quad.addAction(my_action)