In Tiger when I wanted to make icons of a folder I used a little script called ‘Icon Creator’. It didnt work anymore in Leopard. While experimenting I discovered a very fun and easy way to make icons in Leopard.
All you have to do is to open a jpeg (I believe any format that will open works) in PREVIEW.
Then (with the selection tool) you select the part of the picture you want as your icon. Now COPY it (press Comand + C)
Select a folder (or anything you want to change the icon of) and Right-click on this folder, bringing up the info pane. Go up to the top of the pane, click once on the icon to highlight it, and PASTE.
You now have your new icon.