i use this code for navbar on bootstrap 3.2.0, the image should be at most 50px high, or else it will bleed the standard bs navbar.
Notice that i purposely do not use the class='navbar-brand' as that introduces padding on the image
<div class="navbar navbar-default navbar-fixed-top" role="navigation">
<div class="container">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-ex1-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="" href="/"><img src='img/anyWidthx50.png'/></a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse navbar-ex1-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">Active Link</a></li>
<li><a href="#">More Links</a></li>
</ul>
</div><!-- /.navbar-collapse -->
</div>
</div>