If you're comfortable with doing some digital editing, you can get Christmasy clipart online.

I have some beach-Christmas clipart that I've used, but if you google "Santa beach" or "Christmas beach", you'll find tons of pix that you could print out, or even print out right on your background paper using copy/paste. That way you could combine the two themes.

Just be sure to have a good antivirus program running when you google...and be prepared for the fact that everything isn't G-rated, but depending on your privacy settings, you shouldn't get anything too racy...unless that's how you have your privacy settings set.