Query para ser executada direto no Banco.
Como remover todas as imagens dos produtos no Magento 2
truncate catalog_product_entity_media_gallery_value;
truncate catalog_product_entity_media_gallery_value_to_entity;
delete from catalog_product_entity_media_gallery; # 9 sec
delete from catalog_product_entity_varchar where attribute_id in ( select
attribute_id from eav_attribute where attribute_code like "%image" and
entity_type_id = 4 ); # 23 sec in our case (20000 Products)