No theme, unless you consider family traditional trees a theme. I have ornaments my kids made, ornaments from my grandmother, ornaments I bought over 20 years ago when I took over tree decorating from my grandmother. I have lost family members thru the years, so I have a peice of the ribbons from their flower arrangements on my tree. It makes me feel like they are still there in spirit celebrating the holidays with me. I have some of my mothers favorite ornaments and ornaments that remind me of family members and events. No theme. For me Christmas is a time of family, friends and all loved ones sharing in the spirit of the season. Thats what my tree reflects. I will try to post pictures for all to see.
I do like themed trees. They are very nice and really neat to look at. But, they are not for me. I saw a pink and white barbie tree one year and thought that was the cutest thing. I saw a black tree in walmart covered with those bronze colored ornaments. That was beautiful. So to each his own. Whatever brings you joy and happiness is what its all about.