Dropdown with images in navbar bootstrap

I'm having a layout dropdown problem in bootstrap, this dropdown is inside a navbar

html code:

        <nav class="navbar navbar-default navbar-fixed-top" role="navigation"><!--------- START Navbar --------->
        <div class="container">
            <div class="navbar-header"><!-- START Brand and toggle get grouped for better mobile display -->
                <button class="navbar-toggle" type="button" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1"> 
                    <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="#">Meu Site</a>
            </div><!-- END Brand and toggle get grouped for better mobile display -->
            <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1"><!-- START Collect the nav links, forms, and other content for toggling -->
                <ul class="nav navbar-nav navbar-right">            
                    <li class="dropdown">
                        <a href="#" style="padding-top:0;padding-bottom:0" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">
                            <img src="../../../images/icon/share-icon.png" 
                            alt="share"/>
                        </a>
                        <ul class="dropdown-menu" role="menu" style="min-width:80px;">
                            <li style="width:50px;">                                    
                                <a href="#"><img src="../../../images/icon/twitter-icon.png" 
                                alt="twitter"/></a>
                            </li>
                            <li style="width:50px;">                                    
                                <a href="#"><img src="../../../images/icon/facebook-icon.png" 
                                alt="facebook"/></a>
                            </li>
                            <li style="width:50px;">                                    
                                <a href="#"><img src="../../../images/icon/tumblr-icon.png" 
                                alt="tumblr"/></a>
                            </li>
                        </ul>
                    </li>
                </ul>
            </div><!-- END Collect the nav links, forms, and other content for toggling -->
        </div>
    </nav><!--------- END Navbar --------->

the result:

I added Paddings images (50px) so that it has the exact size of the navbar (50px) but unsuccessfully (it gets a gray frame around), and the size of the icon space is also not 50px image)