Under Computer Configuration -> Preferences -> Folder Options, I accidentally added an exe file type and now the icons for all the exes show up the same. How do I restore all the application icons back to their defaults using Group Policy? Deleting the setting does not make it revert back.
I had to set the registry key [HKEY_CLASSES_ROOT\exefile\DefaultIcon] to "%1" using Group Policy and the icons reverted back to their defaults. For some machines, I also had to force Windows to rebuild the icon cache.
Reference: http://filext.com/faq/broken_exe_association.php
There probably isn'y a way to do it with GP. Each icon is specific to the application it's packaged with, if the developers included an icon. For Windows executables, most icons come from shell32.dll. I'm guessing that the best you could do would be to globally replace all of the icons with another icon.
I agree with @joeqwerty. You've basically taken out all the individuality from the icons that were packaged from the software developer.
The only way you might be able to fix this is with a system restore, one computer at a time. I hope this is a small network.