Inserting multiple images Tkinter

I'm having trouble inserting multiple images in a Listbox Widget for tkinter. When I'm inserting the new image, the previous one is gone. What should I do? Here is the code I'm having trouble with:

img = PhotoImage(file = Client.dir + "emo1.gif")
self.listBox.insert(END, sender)
self.listBox.image_create(END, image=img)
self.listBox.insert(END, "\n")
self.listBox.yview(END)