Spells which effect an area (e.g. ice storm) tend to have a set damage regardless of how much of the creature’s body is within the effected area.
Intuitively (I know this isn’t how DnD always works) if a 5ft square of a creature’s body within the area being bombarded by ice shards causes them to take 2d8 damage then, for a large creature, having two or more 5ft squares being bombarded you would expect them to take more damage as more ice hits them.
The question isn’t “does ice storm work this way” but are there any methods of dealing damage that do work this way? Taking creature size into account when calculating how much damage would be taken?