I know this post is old but I reorganized the sprites in the Join Avenue editor. The tool only goes up to 255 but there are definitely more past that number. I don't personally know how to access those sprites but here's the ones that the tool goes to.
https://docs.google.com/document/d/1p0bT8VIZt5KB86Bt-vSUbjA_AL0Fhr1ZUKFKMI8VWTM/edit?usp=sharing