You could always go for the cliché and put a Santa hat on one of them. But here are some much better ideas. I find this site quite useful for getting ideas sometimes.
http://www.istockphoto.com/photos/Pugs?facets={"34":["1","7","8"],"35":["Pugs"]}#fcf1c0e
Though honestly, I think this one is not half bad and more than just the usual cliché!