(dynamic) product thumbnails

Either override templates to change thumbnails: http://docs.woothemes.com/document/template-structure/

OR (better) use the filters:

woocommerce_in_cart_product_thumbnail

and actions:

remove_action( 'woocommerce_before_shop_loop_item_title', 'woocommerce_template_loop_product_thumbnail', 10 );

Once thats removed you can hook in your own action function.