Apple Transactional TV Specification 5.3.6

You can now include alternate audio tracks for Audio Description (AD). These must include a <locale> tag specifying the language, and the AD file locale must match the locale of the corresponding source audio.

Upcoming requirement for artwork locales

Locales for TV season cover artwork, including 1:1 and 16:9 artwork, will be required soon. Start to include locales for your artwork now in iTunes Connect and through Transporter.