gistfile1.php

<?php
add_action( 'admin_bar_menu', function( $wp_admin_bar ){
	$args = array(
		'id'      => 'your-logo',
		'title'   => '<img style="padding-top:5px;" src="' . plugins_url( 'img/your-logo.png',  __FILE__ ) . '" />',
		);
	$wp_admin_bar->add_node( $args );
}, 0 );
add_action( 'admin_bar_menu', function( $wp_admin_bar ){
	$wp_admin_bar->remove_node( 'wp-logo' );
}, 100 );