<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="container">
<nav class="navbar navbar">
<div class="navbar-header">
<button class="navbar-toggle" type="button" data-toggle="collapse" data-target=".js-navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#"></a>
</div>
<div class="collapse navbar-collapse js-navbar-collapse">
<ul class="nav navbar-nav">
<li class="dropdown mega-dropdown">
<a class="dropdown-toggle text-uppercase" data-toggle="dropdown">Mega - Dropdown<span class="caret"></span></a>
<ul class="dropdown-menu mega-dropdown-menu">
<li class="col-sm-4 ">
<ul>
<li>
<div class="menu-item row" onmouseover="setImage(this,'http://placehold.it/150/ffffff/cccc00')" onmouseout="setImage(this,'http://placehold.it/150/ffffff/000000')">
<a href="#">
<img class="col-xs-3 col-sm-8 col-sm-offset-2 img-responsive" src="http://placehold.it/150/ffffff/000000">
<p class="col-xs-9 col-sm-12 bold">Link 1</p>
</a>
</div>
</li>
</ul>
</li>
<li class="col-sm-4 ">