Calibre has a brilliant way to do user overrides that keeps them safe
ish from program updates:
In your case you want to do Icons.
Just put the same EXACT
named icon into the configuration folder
Code:
C:\Users\<yours>\AppData\Roaming\calibre\resources\images
If Calibre finds an override, it uses that instead of the one in Program Files.
Note: You can't change the where used, just the looks.
so the all the places the 'columns' icon is used, will just get the override icon.