What about dithering for the smallest possible images? I'm talking in the 300 byte - 2kb range here. Does anyone have any suggestions for what to do to really get file size down?
Error diffusion causes problems for certain color palettes, but usually results in a smaller image size.
I've made a tool for doing this: https://doodad.dev/dither-me-this, you can easily half the size of a jpeg by dithering it and exporting it as a png.
I’m currently exploring this for my own applications, compressing large 8bit sprite sheet images, and it’s producing much smaller images than most palette based image formats (GIF, WebP, PNG, etc). Follow my progress here: https://twitter.com/mattdesl/status/1346048282494177280?s=21