Iconographer is a fully-featured icon editor. It allows you to both change the icons of items and to edit the icon resources used by various programs. Iconographer has been created from the ground up to deal with many icon formats, including: classic Mac OS (8-bit icons only), Mac OS 8.5+ (32-bit icons with 8-bit masks), Mac OS X (128 × 128 icons in .icns files), Windows and Windows XP (.ico files), and Mac OS X Server (48 × 48 icons in .tiff files).
Note from the developer:
"It was formerly $15 shareware. If you would like to use it and turn off the registration reminder, you can "register" it with the name "Iconographer is now free" and the registration code "HG066414" (if I can manage to build it again, I will look into removing the registration code entirely)."
OS X and OS 9.x downloads available on the homepage:http://www.mscape.com/