Rules (fashion styles) of AltBoobWorld. See comments for brief list, but basically please don't be posing in underwear or lingerie, please don't be fully topless (must be clothing + boobs) and please don't clumsily roll up your top or pull it aside.
(very) Retro AltBoobWorld : The Countess of Somerset. But is she actually wearing an open-fronted dress? The shape suggests she is, though she also has shoulder-boobs. Perhaps it's the corset.