I have always like the social & psychological aspect of larger breasts in society.
Many times I've been surprised at how the amount of mammary tissue a person has affects their interactions with others, how others interact with them, concepts of self-worth, etc.
It is not an aspect of pride or bragging in most cases but rather a "situation" to overcome or reach some sort of balance in a person's experiences. Thus themes that I would find interesting would include:
Shocked Onlookers - (the focus is on the circumstance, there just happens to be boobs)
Comparison Images - (but in context, like sibling rivalry, odd-girl-out, family portraits)
Jealous Neighbor - (the grass is always greener...)
Oblivious to your own assets - (You grow accustomed to what is actually atypical)
Additionally I enjoy anything that has a funny undertone when it comes to body image. Sometimes this is a result of circumstance, or sudden discovery and realization or just simple observation. These are the hallmarks of humor:
Big Boobs "causing" Problems - (the funny side of being busty)
Velma & Daphne Effect - (the nerd girl is actually the appealing / approachable one)
Advantage: Large Chest - (the secondary benefits of an ample front)
Boobpers - (Bloopers, just with more boob - movie, stage, TV scenes derailed by Boobs - possibly with quotes)
Lastly, I would like to emphasize that the female form has been a potent inspiration over the course of human history. The Arts have celebrated and denigrated femininity for centuries. So, for a more cultural / artistic angle I suggest:
Historic Images - (Then had boobs back then, i.e. vintage photos, Civil War, 1800s, etc.)
Recreate Famous Works of Art - (Mona Lise, Girl with the Pearl Earring, The Muses, etc.)
Filter me baby! - (Run multiple filters on a busty image to create a more artistic feel)
Vintage Montague - (Modify a modern fashion model, personality, cartoon character, etc. to look like a particular historical / cultural era)
for example: Cindy Crawford as a busty Japanese Geisha from 1915.