The BPG image format, developed by Fabrice Bellard, is a good alternative to the ubiquitous but very old JPEG. Using the HEVC encoding/compression algorithm, it can store images with a better quality per byte than jpeg, webp or png. It also allows loseless compression, embedded metadata, and alpha channel. As a big bonus, HEVC enc/dec should be supported by video hardware in the near future, so the most time consuming processes will be vastly accelerated.
This is a (linux) Gimp plugin that uses his libbpg library to import BPG files. The encoding part (data to BPG) is not yet included in the library, so there is no export function in this plugin.