Beware! You cannot modify C:\Windows\system32\shell32.dll
and some other system files because it will affect the digital signature and make Windows not boot! You can safely modify the following files:
C:\Windows\SystemResources\batmeter.dll.mun
(contains battery and power icons, usable only for a laptop or tablet)
C:\Windows\SystemResources\imageres.dll.mun
(contains most system icons, not sure about the taskbar icons though)
C:\Windows\SystemResources\SndVolSSO.dll.mun
(contains sound icons)
C:\Windows\SystemResources\Stobject.dll.mun
(contains the USB safe removal icon)
C:\Windows\System32\pnidui.dll
(contains network icons, not available in Windows 11 24H2)
In Windows 11 the power, sound and network icons are grouped together. This ignores any customization. You must ungroup them in order to see your custom icons. I use Explorer Patcher to ungroup them.
In Windows 11 24H2 the network system file is not available, but if you have Explorer Patcher installed you can modify this file instead to customize the network icons:
C:\Program Files\ExplorerPatcher\pnidui.dll
To answer you question, the icons you are looking for might be in the C:\Windows\SystemResources\imageres.dll.mun
file but I am not sure. Once again DON'T modify C:\Windows\system32\shell32.dll
or Windows won't boot!