This screenshot is of my photo library landing page:
You may notice that there are no thumbnails on these items. That wasn't the case yesterday. No matter how many times I set the thumbnails for these libraries, any update kills them. I've seen this reported several times over the past couple of years. Today we get the biggest update to the Photo libraries, and what did you choose to do? Fix functional bugs like this, or make it look nicer? (Hint: the functional bugs are still there.)
May I suggest that your priorities are not in order? X(