Modificar el logo de la pantalla de inicio de sesión

    WordPress 5.2 incorporó un nuevo filtro que nos facilita esta tarea.

    <?php
    /**
     * Custom login form logo link title.
     * 
     * Requires WordPress v5.2+ in order to use the login_headertext filter
     */
    function acme_login_logo_image( $login_header_text ) {
     
        $logo_url          = 'YOUR_IMAGE_URL_HERE';
     
        $login_header_text = ''; // clears default output.
        $login_header_text = '<img src="' . $logo_url . '" alt="' . get_bloginfo( 'title' ) . '" />';
     
        return $login_header_text;
     
    }
     
    // Add filter if WP version is 5.2+
    if ( 5.2 >= get_bloginfo( 'version' ) ) {
        add_filter( 'login_headertext', 'acme_login_logo_image' );
    }