Where does this icon come from? Is there composite icons in Windows?

Version 1909 Build 18363.657

If you assign an unknown file-type, say .test, to mspaint.exe using the normal 'open with' dialog. The file takes an icon that is a white page with the mspaint.exe icon in the middle.

This icon can not be found in mspaint.exe and I've used Nirsoft's IconsExtract, FileTypesMan and ResourceExtract to search for it but have not found this icon.
Of note is that for image files .bmp, .jpg and .png it shows this icon

Also not in present mspaint.exe.

This is why I ask if Windows makes composite icons for certain programs?
The reason I ask is that I would love to make use of such functionality in my own programs so I only have to include a single icon resource (yes, I'm lazy like that )

Thanks for your expert help.

dalchina said:

Hi, the icon is here:
%systemroot%\system32\imageres.dll,-70

I'm seeing this:

That is not any of the icons I am looking for. Even though they are a part of it.
How do they combine with the white paper in %systemroot%\system32\shell32.dll,-1 ?
I see shell32.dll,-63008 and shell32.dll,-16823
But that still does not explain where the mspaint.exe icon on white paper is.