We have a red and white theme, with some silver and clear 'glass' (plastic!) in there, too. Personally, I love having it all match and look like it belongs together, but don't stress if the odd thing is out of place - we have a couple of things now which Hayden has made, and I crocheted a TARDIS to help hubby get in the Christmas spirit last year!
I tend to buy most of my decorations from the supermarkets. Sainsbury's usually have some lovely things.