How to change header image dimensions on twenty seventeen theme (on pages other than home page)

Please paste below code to your header.php file,

<?php 

    if (!is_front_page() ) { 
         echo '<style>.custom-header {height:500px;}</style>';
         } ?>

This code will check if current page is not home page then it will assign a new height to the header image. Change the value according to your wish