Use a state model
Just have an integer state that can be 0,1,2…
It represents the visualization
In draw() just use switch(state) … break… }
to evaluate it.
To change it just use a random timer and set state to a random value
state=int(random(9));
timer ::
if(millis()-startTime>randomMillis) state = … as above
the vars you have to declare and set