Pigi

Using this small plugin you’ll be able to change:
<ul>
<li>Wp-admin </li>
<li>Wp-login</li>
<li>register</li>
</ul>
Logo
You need to insert your custom logo URL and Enable the Function
In the “0.5” Version you will also able to change the Default “Wp-admin” Link (to wordpress.org) with your Own Home Page Link, simply 
setting the custom url from the dropdown menu.
Edit Your Wp-login background
You do not need to do any other change.
<ul>
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</ul>

Login Logo Customization

Change Your Wp-Admin, wp-login Logo, Custom Link And BACKGROUND

Horendra

“Custom Login Page Logo” is a very light weight, handy, easy to use, simple layout plugin that lets you change wordpress logo that you see on login page.
When you create your website, the wordpress uses it’s own logo for login page (wp-admin) which looks very unprofessional but when you use this plugin then you can add your own logo of the company/agency which looks more professional and match with your brand.
You can always change it whenever you want.
<h3>Features</h3>
<ul>
<li>Very light weight, handy, easy to use, simple layout.</li>
<li>Secure, Translation ready ( English and Hindi only ).</li>
<li>Can change wordpress default login page Logo.</li>
<li>Can add logo height and width with unit.</li>
<li>Can add link to the logo for redirect to anywhere on the web.</li>
<li>Can add shadow to the logo.</li>
<li>Can add logo padding.</li>
<li>Can add logo border radius.</li>
<li>Doesn’t impact on your website speed.</li>
</ul>
<h3>Translation</h3>
This plugin is translation ready for English and Hindi language.

Custom Login Page Logo

A simple, secure and very light weight plugin to change wordpress logo that you see on the login page (wp-admin) with rich features.

Login Logo Customization vs Custom Login Page Logo