Fabrice Bellard (of ffmpeg, Qemu and other fame) has proposed and provides a free implementation of a still image format and codec based on the HEVC video codec standard.

BPG (Better Portable Graphics) is a new image format. Its purpose is to replace the JPEG image format when quality or file size is an issue. Its main advantages are:

• High compression ratio. Files are much smaller than JPEG for similar quality.
• Supported by most Web browsers with a small Javascript decoder (gzipped size: 56 KB).
• Based on a subset of the HEVC open video compression standard.
• Supports the same chroma formats as JPEG (grayscale, YCbCr 4:2:0, 4:2:2, 4:4:4) to reduce the losses during the conversion. An alpha channel is supported. The RGB, YCgCo and CMYK color spaces are also supported.
• Native support of 8 to 14 bits per channel for a higher dynamic range.
• Lossless compression is supported.
• Various metadata (such as EXIF, ICC profile, XMP) can be included.
• Animation support.

Find the description, details and links at bellard.org.

For an online comparison of BPG with other still image codecs have a look at this demo.

BTW: Meanwhile, the Daala development team is still struggling to achieve intra-frame encoding on par with HEVC without using patent-encumbered technology.