Faerie (name still pending) was one of my projects as the ASM team leader of SMW Central. It is a multi-functional replacement for the outdated Tweaker and CFG Editor, user-friendly tools used to modify the properties of the sprites in Super Mario World. It was part of my GIEPY standardization project, a long-term plan to move custom sprite insertion to a stable tool called GIEPY.
Faerie is a Java 8 desktop application which can directly edit ROMs and modify sprite configuration files in any supported format, currently just CFG and JSON. Its code is well-documented and is made to be expanded in the future to hopefully provide definitive sprite tweaking for years to come.
Currently, Faerie is in an alpha stage and lacks a lot of its promised features. Development is halted until the situation with sprite tools is cleared up. The public beta version is currently in the works and is planned to contain internal changes for improved stability, full command line scriptability, and basic editing of sprite display data.
The entire codebase of Faerie is licensed under the MIT License and can be found on GitHub.