Ah yes, 'tis the season. Why not decorate your piano too? Well, be careful. Pine garland, candles, glass Christmas balls and figurines can put micro scratches in your piano's finish. Christmas cookies and candy won't make your piano play any better. In fact, mice love little crunchy bits of the gingerbread man. Don't let this happen! (If "Tom and Jerry" manage to get inside your instrument, that old cartoon is not going to be very funny anymore because the damage they can cause could cost hundreds of dollars to fix.)
Little crumbs, if nothing else, can create a pricey repair job because the action will probably need to be removed to clear these pieces.
If you have a high gloss, ebony piano, I highly recommend that you decorate everything in the room, but the piano! Glass Christmas balls can break and the fragments can fall into the internal parts of the piano. Candles, candles, candles. Cool it with the candles! Yes, recreating the candlelit room that Mozart practiced in is exhilarating, but you may be playing with fire. Your piano may not love you back when candle wax oozes down into the tuning pin area. This can take hours or even days to have removed by a professional. Use the candles, but keep them off of the instrument. Runners and tablecloths can be creative, but this invites company to use your Steinway as a buffet table.
If you have a vertical, give it a good cleaning and shine up the finish. If you have grand, clean it and prop the lid up. Now decorate the room, but put nothing on the piano. If you're not sure how to clean your piano, call your piano tuner, have your piano tuned for the holidays and get an estimate on a piano cleaning. (If the tuner is already on-site, it should cost under $50 in most cases.)
Now simply place holiday classic sheet music on the music desk.
A word of advice...
"Deck the Halls" (not the piano).