wordpress get_term_thumbnail code example
Example: get term thumbnail
$image_id = get_term_meta( $term->term_id, 'thumbnail_id', true );
$post_thumbnail_img = wp_get_attachment_image_src( $image_id, 'large' );
echo '<img src="' . $post_thumbnail_img[0] . '" alt="' . $term->name . '" />';