New version of Visual Composer plugin has option to stretch the row in the row settings, this will help you to stretch background image.
So we recommend you to update the theme to the latest version and Woocommerce as well.
Before update delete “woocommerce” folder in the directory wp-content/themes/legenda/ and it’ll be reuploaded from a new theme package.
Also update all required plugins http://www.8theme.com/download-plugins/ .
Don’t forget to create back up of your files and database before starting update process!