By now, it is well known that the Prerelease, Launch Weekend, and Game Day events for the three sets of Theros block, Theros, Born of the Gods, and Journey into Nyx, will be part of an unprecedented Magic experience - they will be part of a continuing challenge called the Hero's Path, involving special Vanguard-like Hero cards and Challenge Decks representing wild foes. So far, we only really know about the first test, which is to defeat the Face the Hydra Challenge Deck at the Theros Game Day, with one of the first Hero cards obtained at the Prerelease or Launch Weekend.
But sharp-eyed MTGSalvation.com Rumor Mill user DataLore spotted some images from succeeding quests on the Hero's Path from other sets that were posted accidentally on the Theros product website. Though they've since been taken down, we can glean information about the rest of the block from these pictures.
The three pieces of art from Theros are mostly known - one of them is a picture of Elspeth prepping for battle, for the Prerelease, and the third is of her in combat with a Hydra, for Game Day. But the second was previously unknown - the Launch Weekend image has her lifting her sword in the air in a temple of Heliod to be consecrated - this seems to be the moment when the sun god infused it with his magic and made it into a spear similar to his own weapon Khrusor.
In addition, two Theros card pictures were spotted on the product page proper - an Akroan warrior, probably one of the terrifying, flesh-eating Androphage band that follows Mogis, and a Triton mage conjuring a magic sphere.
The Born of the Gods Prerelease picture is of a horned, sharp-nailed god, covered in blood and looming over a temple with a wicked grin. Clearly this is one of the minor deities of Theros, and more or less proof that the lesser gods will be getting their own cards in Born of the Gods and Journey into Nyx. I'm guessing this is the sinister Mogis, god of fear, who probably represents black and red. The Launch Weekend image is another divinity - a hoplite god with a winged golden helmet that obscures his face, bronze armor, a blue cape, and a shining belt. This is probably Iroas, red-white god of honorable combat. The Game Day image is simply a pair of rampaging Minotaurs.
The only image from Journey into Nyx seems to be from the prerelease - It's Elspeth facing off against a looming Mogis, and alongside her - Ajani, the leonin planeswalker, not seen in the main story since Alara block! His return is the biggest revelation of these pictures.