Hi,
I made a slideshow userscript for fun, nothing fancy, and surely has some bugs, but I decided to share it.
I saved it as a github gist:
https://gist.githubusercontent.com/desadoc/f2c00439331e723f6a4b5a41d89d09a0/raw/4bb1fa320cf12d27f5816d213c134f23f350de70/danbooru-slideshow.js
It works with either Greasemonkey or Tampermonkey.