The other night my husband was saying when we've been married tons of years and die, we'll have all these ornaments from all the years and our kids will fight over them. Hopefully we'll keep it up that long and have lots of memories over the lifetime of our family all on one tree.
The theme was Mod Podge...and I guess rectangles. Not very creative.
2008 our son was born, so I mod podged a photo of our son when he was a week old on a piece of scrap wood. He was a huge baby, and that is a planter shaped like a tea cup we put him in.
For 2010 I just printed a photo from my husband's graduation.
I guess if you've been married a long time it would be hard to backtrack a ton, but it's a fun little tradition to watch grow over the years.