Not everyone wants to celebrate Christmas. As the name suggests, Not A Merry Christmas Icons are a set of icons for all those that say "bah humbug" to Christmas.
The developer says that he simply got bored one weekend and decided to make the Not A Merry Christmas icons. The icons are Cheap Champagne, Drunk Santa, Elf George, Elf Samantha, Ginger Bite, Me In The Spirit, Snowman Chilled Out, Tree On Fire, Turkey Well Done.
To replace a standard icon with one of the Not a Merry Christmas icons, open the Information dialog and copy the image to the clipboard. In Finder, select the icon to be changed, click Information and inserts the new Icon. Alternatively, you can use an application like CandyBar.
If you despise Christmas then these icons are one cynical and humorous way to make your feelings known.