Background image inside a stack in Ruby Shoes

I'm trying to put a background image on the stack, but I can't get it to work, am I doing something wrong? Here's my code

Shoes.app(:width => 550,
      :height => 450) do

#Main container so I don't have to deal with scroll
stack(:width  => 550,
      :height => 450,
      :scroll => false) do
    background(image("img/intro_bg.jpg"))
end

      

        
        
        
      

    

end

I'm trying to avoid showing the scrollbar as the re-size property doesn't work at all: /