I ran into this article on Twitter: https://uxdesign.cc/designing-for-accessibility-is-not-that-hard-c04cc4779d94
I doubt it offers much new to @Jon_Fila and other advanced students of accessibility, but it has already taught me (an accessibility n00b) something new:
adding an empty
<alt>attribute will make screen readers skip it. If you don’t write any alt text, some screen readers will read the file name to the individual
Emphasis mine. That seems like a counterproductive feature in a screen reader, no? Anyway, adding an empty <alt> tag seems like a pretty easy thing to do for unimportant images.