Design thoughts/plans for the elder Olympians so I have to commit to at least some of them:
Hestia was the first swallowed by Kronos, with the most space to work with in his stomach. The time took its toll regardless, and she was in a bad shape when regurgitated. No one knows how or how much she's recovered, because she wears a garb that covers everything save for her soot-blackened hands and her warm smile and has sworn off ever taking lovers let alone a spouse. She's most commonly around 16ft (~490cm) tall.
Demeter suffered for a long time in Kronos' stomach as well, but she gained the divinity of growth and nourishment very quickly, and applied it to herself. What scars remain are overgrown with verdant and golden plants of produce, or soft and smooth like a well baked bread. Only in winter does her skin grow translucent and cracking, and seep with fine droplets of golden ichor that match her golden blade. She's most commonly around 15ft (~460cm) tall.
Hera was damaged like her sisters, but few can remember her as such, as Zeus brought her the rarest ointments and the most esoteric of treatments when courting her. All signs that remain of the strange procedures from foreign lands are dappled feathers adorning her skin and the horns of a cow upon her head. She's most commonly around 15½ft (~500cm) tall.
Hades was the second to last to be swallowed, and would not force his sisters unto fuirther suffering by jostling for a better position within Kronos' stomach. As a result he suffered damage as severe as that of Hestia, fighting the Titanomachy while constantly pushing back creeping death. Taking over the domain of the underworld let him survive, though while his siblings and later wife have helped fix most of the visible damage — he grows black wool for hair and beard, his hands are the talons of a screech owl, and Zeus swears he's seen the whipping tail of a dog once so his legs might belong to a willing beast as well — he garbs himself almost as heavily as his eldest sister so the full extend of his scarring remains unknown. He's most commonly around 20ft (~610cm) tall.
Poseidon was the last one swallowed, but as none of the other siblings were digested, there was little space to avoid consumption. By the time he was regurgitated there was little skin left on him, and his legs were all but lost. With aid from his mother and from then-oceanic Aphrodite he replaced what he could to be able to fight, and once taking over the domain of the seas reformed himself almost entirely with aspects of beings belonging to it — orca, seahorse, devil ray, anemone, urchin, dolphinfish. He's most commonly around 30ft (~920cm) long in his aquatic form and around 13ft (~400cm) tall transformed into a humanoid.
Zeus was never swallowed at all and so he's not corroded to translucency in places the way most of his siblings are. He doesn't look entirely human however, having tested some of the things he obtained for Hera and Hades during and after the Titanomachy on himself. He's rather proud of his crown of horns, his eagle talons, and his dappling of golden feathers, however, since they're marks of further triumph against his father. He's most commonly around 17ft (~520cm) tall.
