ООО «ЭйВиДи-системы»

This plugin allows you to customize the logo on the WordPress login screen. There is zero configuration. You just drop the logo file into your theme WordPress and this plugin takes over.
Note that you should use a transparent background on the PNG custom logo, crop it tightly (no padding pixels) and use a width of exactly and min 312 pixels for best results. Wider images will be downscaled in modern browsers, but it isn’t recommended to rely on that.
This plugin also works in the <code>mu-plugins</code> directory.

SK-Elib

Customize the logo on the WP login screen. Using a custom logo from your WP theme. CSS is automatic!

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.

SK-Elib vs Simple Login Screen Customizer