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JPEG XL seems to be a very interesting alternative to PNG, TIFF and TARGA.

• It's lossless
• supports layers and additional channels (like alpha channel)
• supports 8-bit
• it's royalty free.

According to the JPEG XL Use Cases and Requirements document, this file format has animated image applications and printing in mind (amongst other things like virtual reality)

Here is the JPEG XL reference implementation.

And here are comparisons with other formats.