How do I change the image in a Surface GUI?

I want to change the image on a Surface GUI whenever I a button.

The script is:

script.Parent.MouseButton1Click:connect(function()
    script.Parent.AutoButtonColor = false
    script.Parent.Active = false
    script.Parent.BackgroundTransparency = 0.3
    wait(2)
    script.Parent.Sound:Play()  wait(2) script.Parent.Sound:Stop()
    script.Parent.Parent.Image.Image = ("http://www.roblox.com/asset/?id=156684759")
    wait(60)
    script.Parent.AutoButtonColor = true
    script.Parent.Active = true
    script.Parent.BackgroundTransparency = 0
    script.Parent.Parent.Image.Image = ("http://www.roblox.com/asset/?id=158928904")
end)

Whenever I press the button, the Image on the Surface GUI goes white. I waited for a minute however the image didn't show.