The ability to customize the WordPress Login Form is included in WishList Member 3.1 and higher. This can be found in the Advanced Options > Logins > Styling section of WishList Member.
Options like removing the WordPress logo, changing the background color, adding an image, etc. are available.
This will also style the WordPress Lost your Password page.
A number of Templates are included and can be used to quickly and easily customize the WordPress Login Form.

Below is an example of a WordPress Login Form that has been customized using one of the available Templates.

There is also a Custom CSS option for those who like to work directly with the CSS code.
This video provides an overview of the WordPress Login Form Custom Styling
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The video below provides additional details on customizing the Custom CSS for the WordPress Login Form:
More information regarding the mobile view of the WordPress login form can be found in the WordPress Login Form Custom Styling – Mobile View Knowledge Base article.