I have used Irfanview as my image viewer for many, many years, and one thing that it does well is customize the windows explorer icons for supported file types through an icons.dll file. There is a good explanation of how to make this work at emiliolab.

Windows 7

There are two problems that I had with this explanation on Windows:

1. you cannot write to anywhere inside C:\Program Files (x86) without administrator permissions, so 7-zip fails to extract the icons.dll to the Plugins directory. Extract the file to the desktop instead and copy it manually.

2. Irfanview needs administrator permissions to set the icon for a file type (it has to write to the registry). So in order to change the preference, start Irfanview by right-clicking it, and select “Run as Administrator”.