There are some interesting psychological insights into chastity here. The beauty who is striking a pose to elevate her slave's arousal makes a good point. What if the guy had a fetish that a woman could take advantage of? Just think of a breast lover's frustration if a busty gal kept him locked while showing off her assets.
Yes, breast fetishism comes up a lot ... I have a lot of pics that would work. But I am always careful to try not to "play to the script": I dislike having the photo completely dictate the story. For instance, I avoid photos of women holding chastity devices: the script has effectively already been written. Similarly, if there is something about a photo that makes it so obviously taken for a particular fetish, I find that a distraction from the writing process. Large breasts can fall into that category sometimes.