For more modularity and in case you have many background images that you want to incorporate wherever you want you can for each image create a class :
.background-image1
{
background: url(image1.jpg);
}
.background-image2
{
background: url(image2.jpg);
}
and then insert the image wherever you want by adding a div
<div class='background-image1'>
<div class="page-header text-center", style='margin: 20px 0 0px;'>
<h1>blabaaboabaon</h1>
</div>
</div>