Placeholder icons show instead of normal icons all over the place

[buckingham2015]

Hey guys, I updated to High Sierra the day it came out. Ever since, I have random icons in random places turning into the placeholder icon. Sometimes the icons load normally, sometimes they don't. For example yesterday the Safari icon was a placeholder in my dock, then after i ran "killall Dock" in Terminal, Safari icon went back to normal, but now the Mail icon was a placeholder. I've attached some examples.

 

[Kornelis]

Could be that the icon cache is corrupted. You can try to boot in safe mode, this way that cache will be deleted.

See here:
https://support.apple.com/en-us/HT201262