Here you can find some changes from the original plugin to allow dynamic URL. Instead of use the absolute path to the logo you can use...

// Original plugin
http://example.com/wp-content/themes/my-theme/assets/img/logo.png

// Changes
[site_url]/wp-content/themes/my-theme/assets/img/logo.png

... and you will have the imagem path according your site_url() value.

Original Plugin URL: https://wordpress.org/plugins/my-wp-login-logo/

• Contributors: afsalrahim
• Donate link: http://labs.afsalrahim.tk/wordpress/plugins/donate/index.php?ref=mywordpressloginlogo
• Tags: wordpress login logo, custom logo, login page logo, logo changer, change login page logo
• Requires at least: 3.0.1
• Tested up to: 4.1
• Stable tag: 2.0
• License: GPLv2 or later
• License URI: http://www.gnu.org/licenses/gpl-2.0.html

My Wordpress Login Logo lets you to add a custom logo in your wordpress login page instead of the usual wordpress logo and customize your login page.

My Wordpress Login Logo lets you to add a custom logo in your wordpress login page instead of the usual wordpress logo and customize your login page.

It also allows you to specify the height and width of the logo. Apart from that you can also customize the login form by adding a custom message below login form and also provide some cool fade in effects for the login form. By adding your custom logo in your login page, you can make your website more professional and also impress the guest bloggers and other users who view these pages.

This section describes how to install the plugin and get it working.

1. Upload the plugin.
2. Activate the plugin through the 'Plugins' menu in WordPress
3. Upload your desired logo using the WordPress media uploader and copy the uploaded image's File URL path.
4. Click the My Wordpress Login Logo and paste the uploaded image's File URL path in the Logo URL field provided.
5. That's it! You can now logout and check your yousite.com/wp-admin/ or yousite.com/wp-login/ page to see the changes.

1. Upload your desired logo using the WordPress media uploader.
2. Copy the uploaded image's File URL path and input it in the Logo URL field.
3. That's it! You can now logout and check your yousite.com/wp-admin/ page to see the changes.

Simply input your desired logo height and width in the given fields to change the displayed logo size.

Less than or equal to 320px width and 70px height is the recommended logo size for your Wordpress Login Page.

1. My Wordpress Login Logo Settings Page
2. Wordpress Login Page

• Add Custom Message below Login Form feature added.
• Customize Login Form using a Fade In effect.
• CSS Fix for smaller size logo images. Thanks to Valentins Ivanovs for the css fix.

• Implemented the option to edit the image link