Is there a function for random image spawn

I'm making a space invader game and I would like to have different invaders spawn. I made the GIFS now I'm just stuck on how to create the RANDOM function so different invaders spawn at random times.

I hope I'm clear enough.

turtle.register_shape("L.gif")
turtle.register_shape("D.gif")
turtle.register_shape("M.gif")
turtle.register_shape("R.gif")
turtle.register_shape("Meta.gif")

#Choose a number of enemies
number_of_enemies = 5
#Create an empty list of enemies
enemies = []

#Add enemies to the list
for i in range(number_of_enemies):

#Create the enemy
enemies.append(turtle.Turtle())

for enemy in enemies:
  enemy.color("red")
  enemy.shape("L.gif")
  enemy.penup()
  enemy.speed(0)
  x = random.randint(-200, 200)
  y = random.randint(100, 250)
  enemy.setposition(x,y)