Adding an image to the nav bar

This is a plugin that makes it easy to add icons or images as menu item:

Menu Icons

I use it myself for icons. But there is also an option to add images....

Maybe you can use this

To add an image to the menu, you can use a function like this:

add_action('generate_inside_navigation','generate_navigation_logo');
function generate_navigation_logo()
{
?>
	<div class="site-logo">
		<img src="THE URL TO YOUR IMAGE" alt="" />
	</div>
<?php
}

Then add this CSS:

.main-navigation .site-logo {
    float: left;
    line-height: 60px; /* Adjust this to your menu item height */
    margin-right: 1.5em;
}

Adding PHP: http://generatepress.com/knowledgebase/adding-php-functions/
Adding CSS: http://generatepress.com/knowledgebase/adding-css/

Hope this helps :)