Mark Jaquith

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 WordPress content directory, named <code>login-logo.png</code> and this plugin takes over.
Note that you should use a transparent background on the PNG image, crop it tightly (no padding pixels) and use a width of exactly 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.

Login Logo

Customize the logo on the WP login screen by simply dropping a file named login-logo.png into your WP content directory. CSS is automatic!

Harish Chouhan

Themeist Co

Custom Login Logo lets you replace the default WordPress login logo with your own — no need to touch code or upload files via FTP.
Just activate the plugin and use the built-in media uploader on the settings page to upload your custom login logo. It’s quick, simple, and works with most themes.
This plugin is perfect for branding client sites, personalising the login screen, or maintaining a consistent visual identity.
Features: 
– Upload your custom logo using the built-in WordPress media uploader 
– No need for FTP or coding 
– Works with most themes and setups 
– Retina/high-DPI image compatible 
– Lightweight and fast
If you find this plugin useful, please consider leaving a 5-star review on WordPress.org.

Custom Login Logo – Easily Add a Logo to Your WordPress Login Page

Easily add a custom logo to your WordPress login page using the built-in media uploader.

Login Logo vs Custom Login Logo – Easily Add a Logo to Your WordPress Login Page