Thanks @nago- and @lifning for the Hackers post and the base ffmpeg command tricks.
Here I used
ffmpeg -i interstella.mkv \
-c:v libwebp \
-r 12 -s 80x64 \
-lossless 0 \
-compression_level 6 \
-quality 0 \
-preset picture \
-loop 1 \
interstella.webp
ffmpeg -i interstella.mkv -vn -acodec mp3 interstella.mp3
(where the .mkv is a copy of my physical DVD made with MakeMKV)
And I encoded the mp3 file with XLD into a 20kbps AAC file to barely fit at the 10MB mark for each
