PIXI
From SnesLab
PIXI is a sprite insertion tool created by JackTheSpades and later maintained by Tattletale (no longer working on it). It is used to assemble and insert regular sprites, generators, shooters, cluster sprites and extended sprites in Asar format. It also has the ability to load certain sprites in a per-level basis, allowing for a nearly limitless amount of custom sprites such as enemies, obstacles, bosses, etc. in one's game.