I've always left the icons alone as regards file types. However, for icons on my desktop (win) or for links on the start bar, I make my own using Microangelo. Quite a fun lil program. In fact, I made one for my perlmonks.com link... a "p" with a little halo.
_____________________________________________________mojobozo
word (wûrd)
interj. Slang. Used to express approval or an affirmative response to
something. Sometimes used with up. Source