Apple Bottoms

 There are a couple of reasons the Apple sisters end up in more of my spanking pictures (and pictures in general) than most of the other Equestria Girls characters.

One is definitely the country setting making the use of corporal punishment more believable, and the things that come with that setting like sheds, switches, etc. 

Another factor is that there simply are more of them; they have a large family both immediate and extended. Also the fact that Big Mac is one of the few male characters and introduced in the first episode, AJ is a middle child so can both give and receive discipline, Apple Bloom is younger so means more school pics, her friendship with Sweetie and Scootaloo and her closeness with her cousin Babs, the feud with Diamond and Silver Spoon, and so on. All of this adds up to it making more sense for Applejack to administer spankings than Fluttershy, even without their personalities.

Of course Twilight has a big family and is (sort of) a middle child (acting as some kind of amalgam of teacher/big sister/surrogate mother to Spike), and Rarity has both a younger sibling in Sweetie and parents so can similarly give or receive (and through Sweetie, connections to Apple Bloom and Scoots). Which is why I have made use of those relationships and will continue to explore options. As for the third member of the CMC, Scootaloo does have a surrogate big sis in Rainbow Dash, and...watch this space!

In general, though, I do expect the Apple family to have the most pics, followed by Twilight and Rarity 's families.