I only really theme my trees by colour, I have always used red and gold in the past, and have usually only one tree but my ideal would be 3. One in the living room, one in the family room and one more either in the dining room or hallway.
My living room needs a major overhaul - the plaster needs to come off the walls and the ceilings need to be replaced. It definately won't be done by christmas so I will use my usual red and gold theme.
We are currently working on another project (family room and laundry) which I am hoping will be completed before Christmas. So my plan for a red and silver tree in the family room may become a reality, will have to see.
I am in the process of collecting some plum and silver decorations for a tree either in the hallway or dining room.
I do have a snowman theme in my kitchen and I have to say this is my favourite. I absolutely love snowmen.