Wordpress - Getting a taxonomy's thumbnail url

The images where setted by woocommerce,

In case someone needs, this is how I did it

$thumb_id = get_woocommerce_term_meta( $term->term_id, 'thumbnail_id', true );
$term_img = wp_get_attachment_url(  $thumb_id );

Taxonomies don't by default have thumbnail images. Without knowing how those are set I can't say exactly how to get the thumbnails, but as for "what am I doing wrong?" get_post_thumbnail_id accepts a post ID or lacking that assumes the current post in the Loop. You are passing it a term_id, which isn't going to work. You can see that in the source:

32  function get_post_thumbnail_id( $post_id = null ) {
33          $post_id = ( null === $post_id ) ? get_the_ID() : $post_id;
34          return get_post_meta( $post_id, '_thumbnail_id', true );
35  }

I suppose, if the term_id happens to match a post ID you'd get something but it isn't going to be what you want or expect.