It's bugged me for awhile that when working with Blackmagic RAW on Linux you wouldn't get thumbnails...
Went on a bit of a tangent today and boom, turns out it's not that difficult to implement - at least in nemo and nautilus, dolphin isn't playing nice yet.
@micahbp I've put it up on GitHub 👀. I can't believe it took me this long to find out about the /usr/share/thumbnailers directory.