The magician shows a stack of brightly-colored Christmas cards, as if pieces of a puzzle. These are shown one at a time and placed back into the stack. The cards are scattered and bundled up... and, the next moment... the individual cards have turned into a single big Christmas sheet!
This is very visual and quite beautiful - and a big surprise for your audience!
At the moment when the large Christmas sheet appears, your audience will yell, "Wow!" This trick makes the performer look especially good!