ResExcellence has a VERY cool guide to enabling multiple icon sizes in a single Finder window or on the Desktop - you can set the size on a PER ICON basis! Don't you just love Quartz?
http://www.resexcellence.com/hack_html_01/05-23-01.shtml
-Membranophonist
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010523133741882