I wanted MyUnity specifically for the ability to have more than 4 virtual desktops, that is really all that I absolutely needed it for. However, then I got to playing with it wanting to customize my themes and whatnot, all was going ok until all my system icons went missing.

That is to say, they're not completely missing, but all folders and files without a live preview show up as a page with a bent-corner. Also, folder icons in the alt-tab popup show up as completely transparent; they still take up room and have a label, just no visible icon. I have tried playing around with myunity themes and icon sets and no matter what I can't seem to get things back to where they were.

This isn't a huge encumbrance but it is starting to get more and more annoying and I feel like I'm missing out in understanding something about how Unity works.

What could have caused this and how do I fix it?

Update: Per a commenter's suggestion I tried running unity --reset-icons. After 15 minutes it was still scrolling by (I assume it was in a loop). Here is what was in my terminal buffer at the time I ctrl+c'ed.