I found the code line into CSS
!I had to search for "jpeg"
Code:
#ipsLayout_header {
border-top:3px solid #4F6B86;
background-image:url('http://img0.gtsstatic.com/wallpapers/e9ffc901b38f7fc7d54e22bdbc5c211d_large.jpeg');
background-position: 0% 50%;
}