They most likely limit image formats to just a few for feature parity across systems. They can be sure that those formats will be handled by whatever library they use in other places, in the future, or on other operating systems. Whereas with less common formats, that might not be the case.

The extension has been working on Edge and Chrome on Windows for a while. You just need to install iCloud desktop for it.

Most likely won’t happen as Apple doesn’t seem to care about Firefox nowadays. FaceTime on the web is not officially supported on Firefox and they regularly break iCloud on Gecko.

Removing the bags around the eyes and making the reflections in them point in the same direction would make it less creepy lol.

Other than that, it looks nice!