Against my better judgement I went to the site and found two critical errors that are issues:
1- You do not have an element with a class of "navbar" or "x-navbar"
<nav id="site-primary-nav">
<ul id="site-primary-menu" class="large-nav sf-menu mobile-menu clearfix sf-js-enabled sf-arrows" style="touch-action: pan-y;">
<li class="MenuJibberJabber">
<a class="sf-with-ul" href="/church/">Church</a><ul class="sub-menu" style="display: none;">
<li class="menu-item-277">
<a href="/ministries/">Ministries</a></li>
<li class="menu-item-278">
<a href="/sermons/">Sermon’s</a></li>
</ul>
</li>
<li class="menu-item-21">
<a class="sf-with-ul" href="/academy/">Academy</a><ul class="sub-menu" style="display: none;">
<li class="page-item-89 menu-item-113">
<a href="/">Overview</a></li>
<li class="menu-item-115">
<a href="/who-we-are/">Who We Are</a></li>
<li class="menu-item-114">
<a href="/llc-vision/">LLCA Vision</a></li>
<li class="menu-item-112">
<a href="/llca-mission/">LLCA Mission</a></li>
<li class="menu-item-111">
<a href="/applicationfees-and-dress-code/">
Application,Fees and Dress Code</a></li>
<li class="menu-item-110">
<a href="/curriculum/">Curriculum</a></li>
</ul>
</li>
<li class="menu-item-47">
<a class="sf-with-ul" href="/community-kids-learning-center/">
Community Kids Learning Center</a><ul class="sub-menu" style="display: none;">
<li class="menu-item-172">
<a href="/cklc-page/">CKLC About</a></li>
<li class="menu-item-171">
<a href="/cklc-hours-and-fees/">CKLC Hours</a></li>
</ul>
</li>
<li class="menu-item-38">
<a href="/contact-us/">Contact Us</a></li>
</ul>
</nav>
I would try applying that CSS using one of these selectors
nav {background-image:...}
#site-primary-nav{background-image:...}
#site-primary-menu{background-image:...}
2- The URL for the background image does not resolve.