I found this code online :

//* Add custom message to WordPress login page
function smallenvelop_login_message( $message ) {    if ( empty($message) ){        return "<p><strong>Welcome to SmallEnvelop. Please login to continue</strong></p>";    } else {        return $message;    }
}
add_filter( 'login_message', 'smallenvelop_login_message' );

But this only adds a line of text to the 

https://ukroofingstore.co.uk/wp-admin

Im looking to modify and add some text even an image if possible here :

https://ukroofingstore.co.uk/my-account/

Any help on how that could be done ?

Ive been criticized for using too many wordpress plugins so I was hoping there was a some code to add too functions.php to do the same.