No other box toppers were shown in the most recent stream, but more variations on existing Magic cards were
Whenever it destroys a creature, it gets a +1/+1 counter
You can sacrifice a good number of lands and then search for Field of the Dead as part of its effect
A new card type, inspired by Final Fantasy summons like Shiva, enters the game with a lore counter, gives an instant effect, and stays for a few turns before vanishing, copying the short but strong nature of summons
And it's a real shame because modal lands with spells ARE a great design
(You may cast cards with retrace from your graveyard by discarding a land card in addition to paying their other costs.) If a spell you cast with retrace is countered, it's put back into your graveyard