Can I get thumbnail of taxonomy?

you can use advanced custom field plugin for better use

 // get the current taxonomy term
$term = get_queried_object();

// here is the taxonomy image
$image = get_field('image', $term);

Or

You can use free plugin in your template

 URL: https://wordpress.org/plugins/wp-custom-taxonomy-image/
 if (function_exists('get_wp_term_image'))

{
$meta_image = get_wp_term_image($term_id); 
//It will give category/term image url 
}

echo $meta_image; // category/term image url