I was playing a bit in these days in extracting some cool images from all Pokemon 3DS games, i can guide you a bit. I'm using pk3DS>Tools>Misc Tools>(un)Pack + BCLIM to decrypt .bin files, Every File Explorer and Kuriimu>Kukkii to see and extract/convert them into .png images.
All pokemon little sprites (box pokemon sprites) are in 0/6/2 (you'll get a folder with 1154 files named dec_0000, dec_0001,...,dec_1153), all items images are in 0/6/1 (you'll get a folder with 769 files named dec_0000, dec_0001,...,dec_768). Still didn't dig to much for big pokemon sprites, i can anyway tell you that in Pokemon Moon you can find all big sprites inside 2/6/9 (you'll get a folder with 855 files named dec_0000, dec_0001,...,dec_854). Let me know!