Chrismas is based on any number of ancient pagan festivals. The winter solstice, Nollaig, on december 21, being the main celtic one, when the sun god was freed from the underworld. We know that stone age man in Ireland hououred this event at least 5,000 years ago, from the passage grave at Newgrange which is only illuminated by the rising sun on December 21.The Romans celebrated a huge week long festival around the solstice, in honour of the god Saturn. The tradition of bringing an evergreen tree inside is an ancient germanic pagan custom in houor of the god Baldr, as is the use of miseltoe. The use of holly is associted with holly king of ancient european tradition, who rules from midsummer until mid winter, at which point the oak king takes over.Some people believe that the Holly king, portayed as a jolly old man, corresponds to Santa Claus. The early Christians used pagan festivals to convert pagans...they changed the names and reasons for the celebrations, but kept the festivals so that people would be more comfortable with the changes. I believe it's now accepted as fact by bible scholars that Jesus was born sometime in February, so the festival of christmas as Christ's birth is merely a way of incorporating a much older tradition into acceptable (by the church ) practice.
Christian traditions around Nollaig/Yule have been going on for a long time, they are entitled to their beliefs as much as anyone else. If the December season of joy, celebration and good will extends to both Christians and Pagans , I'm all in favour of that ...Nollaig Shona / Merry Yuletide / Happy Christmas.
There's a book about celebrating Yule as a wiccan by Dorothy Morrison, called Yule; A Celebration Of Light And Warmth link:
http://www.llewellyn.com/bookstore/book.php?pn=K496 Personally I have not read it, but it's been highly recommended to me by several people. I would also try to research those odd local christmas traditions, as these almost inevitably have pagan roots, which you can incorporate into your yule celebrations with a little creativity.