One of the neat things we did this year was get a marquee in our garden off the back glass doors. It was about 6 meters x 5 meters and gave us a lot more usable space. We put space heaters inside with lots and lots of candles so it felt comfortable. We also rented 3 round cocktail tables so people could put their drinks on, food or ashtrays (we seem to have quite a few smokers in the company).
I took these two photos from the marquee looking into the party and thought they looked cool.