For a modern backdrop for your Christmas decorations, try a contemporary grey colour and accessorise with white ornaments for a sophisticated, urban look.  For a really modern feel, if you have a fireplace, consider painting it the same colour as the wall, but remember .... preparation is key and always use appropriate primer undercoats as well as durable, water based, top coats.  If your chosen colour isn't available in the finish you require for your fireplace, you can have it made specially for you at any Crown Colourmixing stockist.