You can change the default icon via Regedit.exe
Locations:
HKEY_CLASSES_ROOT\7-Zip.rar\DefaultIcon
HKEY_CLASSES_ROOT\7-Zip.zip\DefaultIcon
HKEY_CLASSES_ROOT\7-Zip.7z\DefaultIcon
Set the (default) value data as follows:
"C:\Program Files\7-Zip\7zFM.exe",1
Log off and log back in, restart Explorer, or refresh the icons manually.