I do a winter theme - lots of blue and silver and white ... lots of glass and crystal-like stuff that reflects the light. The cats love to watch the prisms of colour and light dance all over the walls, and they go crazy when I light candles - staring at the flickering shadows is a favourite past time. I don't have a tree - probably a good thing since my younger cat would - no doubt - get into all kinds of trouble!
I don't think our dog knows any difference. He did get a new bed from Frontgate as an early Christmas present, though. It's very nice, and very cushy, he seems to like it.