CandyBar has become one of the first casualties of Mountain Lion but the good news is the developer is now giving the dock customization software away for free. Although you can customize icons individually, the application will not allow you to change the look of the entire Dock in Mountain Lion because Apple has changed the way it renders, hence the decision to make it free from now on.
However, it will be pretty much unsupported in the future apart from a few minor updates. The developer has provided the following serial number: PPQA-YAMA-E3KP-VHXG-B6AL-L to activate CandyBar.
With CandyBar, you can create smart lists, drag and drop icons and select whole collections or unique icons. Icons appear in a dark transparent window and you can zoom in or out of them thanks to the slider on the bottom right of the interface. If you don’t like the look of an icon, you can make it look the way you want by simply dragging images in to replace them.