SysIcon is a FREE utility which allows you to change default sets of icons in windows, its not a image editor but performs necessary changes to registry in order to change default icons in windows.
It allows you to change the almost all the shell icons including default folder icon, start menu icon, control panel icon, unknown file type icon, my computer icon, drive icon, network icon and lot more other system icons can be changed.
You can also change the shortcut overlay, default run icon, all programs icons etc In short you can use this free program to change the default icons on any thing on windows.
Even after changing the default icon of any thing in windows with this program, you can revert to the default windows icon for that object any time you want also by clicking Reset To Windows Default for the selected object.
Or you can customize the icon of any selected object by clicking the button Relocate icon
This program is free from any kind of adware, spyware or malware and it is 100% free released under GPL. According to me it is the best free program which lets you play with system icons in windows.