These are programs that I have developed and are free to download and use. If you want to link to any of these it would be appreciated if you would also link to its page.
A script-powered graphics file converter.
A wrapper for vgmstream that can convert a large range of video game audio formats.
A program that can swap palettes within a sheet.
Can remove backgrounds from pixel-perfect images.
A collection of miscellaneous tools I’ve created over time that mostly had a very narrow use and aren’t worth releasing individually. Mostly just for archival purposes, but here’s a readme with a program list, it might contain something you’re looking for.