@Skeet just FYI some of the pics you've been posting won't be visible to all members, mainly those with older computers and / or OS's.
If you're still downloading them first to filter out .png files, you should be able to see that some are WebP, which is a format created by Google, first appearing in 2018. It was intended as a replacement for JPEG, PNG, and GIF's.
My rule of thumb therefore is to stick with old formats until they die for maximum compatibility. For example with audio I haven't gone past MP3 and as implied for pics, jpeg.