Hi Damon, and thank you.
The file formats for next-gen formats on the Internet are WebP, JPEG 2000, and JPEG XR.
For WebP, the file extension is .webp and the MIME type is image/webp.
For JPEG 2000, the file extension for JPEG 2000 images is .jp2 or .jpx and the MIME types are image/jp2, video/m2, image/jpx and image/jpm.
For JPEG XR, the file extension is .jxr and the MIME type is image/jxr.
Thanks again. Have a great week!