Tkinter image label not appearing

I have no idea why this doesn't work. I'm using python 3 on a mac. I have tried label.image but it doesn't work. Here's my code:

File=open("/Users/user/Desktop/Python/File.txt")
FileContents=File.readlines()
ThingAmount=Team[0]
ActiveThing=Team[1]
ActiveThingImage=PhotoImage("/Users/user/Desktop/Python/"+ActiveThing+"/"+ActiveThing+".gif")
EnemyThingImage=PhotoImage("/Users/user/Desktop/Python/Enemy/EnemyThing.gif")
ActiveThingLabel=Label(window,image=ActiveThingImage)
ActiveThingLabel.image=ActiveThingImage
ActiveThingLabel.place(x=0,y=0)
EnemyThingLabel=Label(window,image=EnemyThingImage)
EnemyThingLabel.place(x=100,y=100)