Better icon placeholders
When the app icon is missing (in both app grid and multitasking switcher) there is a "image-missing" placeholder icon:
For some reason it's not the correct size though (maybe a HiDPI thing, it looks to be about 1/4 of the canvas), and the icon itself isn't that great for this purpose.
We should ship a dedicated app icon placeholder icon which looks more like a real app icon (e.g. a colorful square with a question mark) instead instead.