allilevine

This plugin adds an options page (Settings > Login Screen) that allows you to customize the WordPress Login Screen (wp-login.php). You can:
<ul>
<li>Upload a custom logo (it will be resized to fit if necessary)</li>
<li>Choose a link color</li>
<li>Choose a link rollover color (defaults to a darker shade of the link color)</li>
<li>Choose a button color (defaults to a button version of the link color)</li>
</ul>
The plugin also links the new logo to your site URL.

Simple Login Screen Customizer

Good

Choose a logo and link color for the login screen.  The plugin will do the rest.

Kerry Webster

Features of the Branded Login Screen plugin:
<ul>
<li>FULL SCREEN BACKGROUND IMAGE</li>
<li>USE YOUR OWN HEADER IMAGE IN PLACE OF THE WORDPRESS LOGO</li>
<li>POSITION LOGIN FORM: LEFT, CENTER OR RIGHT / TOP, MIDDLE</li>
<li>LOGIN FORM IS RESPONSIVE FOR SMALLER SCREENS</li>
<li>SCROLLING OF FORM IF OUTSIDE OF VIEWPORT</li>
<li>BACKGROUND IMAGE SIZES WITH WINDOW RESIZE</li>
<li>REPEATING BACKGROUND IMAGES SUPPORTED</li>
<li>REMOVES ALL WORDPRESS BRANDING</li>
<li>STILL UPGRADE PROOF</li>
</ul>

Branded Login Screen

Update the WordPress Login Screen to use a hi-res, full screen, resizing background image. Now completely responsive.

Simple Login Screen Customizer vs Branded Login Screen