Guys, brace yourselves - I found the solution here: https://mjtsai.com/blog/2019/02/01/clearing-the-icon-services-cache-in-mojave/
In case that becomes unavailable I'll tell you here. Open terminal and type these two commands:
sudo rm -rfv /Library/Caches/com.apple.iconservices.store
sudo find /private/var/folders/ \( -name com.apple.dock.iconcache -or -name com.apple.iconservices \) -exec rm -rfv {} \;
Then restart. You'll see some Spotlight and iconservices-related processes spike for a while as caches and indices are rebuilt.
Note: I also (prior to that) deleted Xcode and and app called I believe "Duplicate File Finder", as per some other potential solutions. Also deleted /Library/Caches/* and selectively deleted folders from ~/Library/Caches based on their disk usage and what I thought I needed to keep. Also deleted ~/Library/Preferences/com.apple.finder.plist and restarted Finder. But I believe that all of this was probably unnecessary to solve the problem.
In case that becomes unavailable I'll tell you here. Open terminal and type these two commands:
sudo rm -rfv /Library/Caches/com.apple.iconservices.store
sudo find /private/var/folders/ \( -name com.apple.dock.iconcache -or -name com.apple.iconservices \) -exec rm -rfv {} \;
Then restart. You'll see some Spotlight and iconservices-related processes spike for a while as caches and indices are rebuilt.
Note: I also (prior to that) deleted Xcode and and app called I believe "Duplicate File Finder", as per some other potential solutions. Also deleted /Library/Caches/* and selectively deleted folders from ~/Library/Caches based on their disk usage and what I thought I needed to keep. Also deleted ~/Library/Preferences/com.apple.finder.plist and restarted Finder. But I believe that all of this was probably unnecessary to solve the problem.
