Vast HTML

This is a full featured plugin to help you edit your login just the way you want it. Lets you use or block the original wordpress 
css (the first plugin to do this). Comes with one pre made style you can use or deactivate. 
Very easy to create your own style using the style tags givin in the plugin. 
Please visit http://vasthtml.com/js/login-xchange-plugin/ for usage instructions.

Login XChange

This plugin will let you change the css of your login and register pages.

shokola

Customize the login page with following settings :
<ul>
<li>Image logo</li>
<li>Link on the logo</li>
<li>Background image</li>
<li>Background position, repetition and cover parameter</li>
<li>Favicon image</li>
<li>Classic or Material style</li>
<li>Light or Dark ambience</li>
<li>Buttons and borders color</li>
<li>Logo background color</li>
</ul>
Also :
<ul>
<li>Removes WordPress logo and version in the back-office</li>
<li>Removes WordPress welcome widget and WordPress News Widget on the back-office dashboard</li>
<li>Automatically check ‘Remember me’ on the login page</li>
<li>Removes ‘Proudly powered by WordPress’ on the login page (mouse hovering on the logo)</li>
</ul>

Shokola Custom and White Label

Set WordPress as "White Label" and personalize the login page. See Settings / Custom Shokola to configure.

Login XChange vs Shokola Custom and White Label