Change WordPress admin login logo, mouseover title and logo url.

wp-login-logo-title-change.php

<?php
// add this to your themes functions.php file
// change login image
add_action("login_head", "tmx_login_head");
function tmx_login_head() {
	echo "
	<style>
	body.login #login h1 a {
		background: url('".get_header_image()."') no-repeat scroll center top transparent;
		height: ".get_custom_header()->height."px;
        width: ".get_custom_header()->width."px;
	}
	</style>
	";
}

// Change title for login screen
add_filter('login_headertitle', create_function(false,"return get_bloginfo('title');"));

// change url for login screen
add_filter('login_headerurl', create_function(false,"return home_url();"));

You'll need to add theme-support for 'header image' as well in your "after_setup_theme" action hook:

        // Add theme support for Custom Header
        $header_args = array(
            'default-image'          => get_template_directory_uri() . '/resources/img/logo.png',
            'width'                  => 140,
            'height'                 => 40,
            'flex-width'             => false,
            'flex-height'            => false,
            'uploads'                => true,
            'random-default'         => false,
            'header-text'            => true,
            'default-text-color'     => '#FFFFFF',
            'wp-head-callback'       => '',
            'admin-head-callback'    => '',
            'admin-preview-callback' => '',
        );
        add_theme_support( 'custom-header', $header_args );