The background image of the home page is not seen

Hello,
I can not get the background image of the home page to display. The image I have in the route:
templates / gk_steakhouse / images / header_bg.jpg
but you do not see anything. As can display the image ?. Appreciate detailed explanation. Thank you.

P.S. My URL is:
http://web1.qualitaweb.es/

Where did you set this image?

I installed the Normal template (not demo). The image is uploaded via ftp to the indicated route. But it does not know how to activate it from within the template. How do you turn? How is it visible?

If you look at the url you can see what happens. Appreciate solution. It took several hours, and I'm desperate.

If you wish, from the basic template, set a background image for the initial page, where is the activation of the specified image?. Appreciate a solution. My URL is:
http://web1.qualitaweb.es/

I just have checked and header background shows correctly.