When I started out in metal clay, one of the first books I read was The Art of Metal Clay by Sheri Habb. In this book is a great silver clay Christmas tree, I can't find a picture of it but it is a fun metal clay tree with a variety of colourful cubic zirconias adorning the tree.
In my search to find a possible picture of this tree, I came across Sheri Habb's website which has lots of fun stuff. One of the holiday themed items she has is a tutorial to make a Santa Bottlecap Pin. (not metal clay but fun holiday themed project and you can modify depending on what you want to celebrate).
Christmas tree by Cindy Pankopf: From www.bnb.jewelrymakingmagazines.com
Also in my search I found some sources for metal clay holiday themed tools:
Metal Clay Supply in the States offers a QuikArt Stencil of a snowman and a stocking.
I get most of my cookie cutters from here in Ontario from Shades of Clay - they have a great selection of cutters.
Remember you can always make your own template. Just draw your design in card stock and cut it out.
Enjoy your week!