1) Size can be potent metaphor for mood. Large can represent feelings of insurmountable power, small the daily struggle to live under the dampener of depression or down-cycle states. It also can reveal the sensual quality of both, e.g. touching the sky or feeling each sensation intensely, even painfully.
2) Having protagonists at different sizes can mirror the subjective relativity of social relations.
3) New and unusual takes on our living environments can revealed establishing a critique of the spaces we live in - making think of Gaston Bachelard's La poétique de l'espace or the Poetry of Spaces
4) Interesting range of challenges for the artist - extreme foreshortening and perspective as well as key artistic challenges such as hands, feet, the whole human being nude and clothed, still lives, townscapes, landscapes, waterscapes, foreshortening, perspective, decoration.
5) All the above enable the artist to subvert comfortable conventional views of reality.