I have often used the trick of "cutting" the icon
from one info window and pasting it into another.
(in OS X)
But once in a while, I find one that cannot be pasted.
In other words, the icon for this item cannot be changed.
I have also noticed that when I make an alias for
an item the alias has a generic item instead of the
same icon as the original. Sometimes, but not always,
I can fix this with the cut-n-paste trick.
Any idea of a cause and or fix for either of these