Critical Message
This foundryvtt module allows you to set custom images and text to be shown in the chat when someone rolls a Nat1 or Nat20. Idea was inspired by the module "sadness-chan", I didn't like it how the message looks and the way selecting images where done. I used some of the lines in that module for the default here.
Default view:
I like to use Chat Portrait module and it looks like this:
Settings are only available to GM, allowing to change folder of images, if you want to select a single image for nat1/nat20, edit the text, reset to defautls.