I'm really not a fan of using the generally unsupported aspects of the file formats. Like sure, png supports alternate compression schemes which in combination with the fully generic datablocks system which I think technically accidentally makes it Turing complete. But its not like any reader ever supports it fully, hell most readers dont support showing the other images in a png file. Its also quite common that palettes aren't properly supported, in particular for uncommon combination. Palettes themselves are also not truly sufficient for what they are supposed to do, as that would require generic scalar to scalar functions. Its like this with every damned old image format. People try to make the format to end all formats and end up accidentally inventing really shitty programming languages with terrible separation of concerns which are terribly supported but work as people only ever use them for single image data.

Another stranger mistake is the use of generic compression a part of the format, its much better to leave that up to the filesystem or stream. I dont really understand why this was ever a good idea, but it certainly hasn't been one for decades.

The more recent blob formats people have developed aren't much better, they still confuse the specification of a single blob with the specification of the container format, and try to be convenient and fully generic at once. If people actually wanted a fully generic dataformat and accepted that this requires a programming language, just let that be python, instead of inventing some shitty new one...