Panel thumbnails for uploaded font files

Others looking for a solution. With help from Bastian, this is how you can achieve what I was looking to do:

"Let’s say this is your setup

example.otf
example.otf.txt
example.oft.png

In example.otf.txt you could set the template:

Template: font

Then add a blueprint:

site/blueprint/files/font.yaml

And in there set the image options like this:

title: Font File
image:
  query: file.siblings.findBy("name", file.filename)

This should work in theory. "

And works for me!