Images that focus heavily on the size difference between two or more people; often minigirl, miniboy, giantess, and giant pictures fall into this category.
If the 'natural' difference in size between characters, ie. 'short' vs 'tall' is the focus of the picture, use height difference instead. If one person has a small body overall, they are petite.
Focusing exclusively on breast size difference is breast envy instead.
For an image that has been changed from its original size, use resized.