A time capsule
Place photos and some small objects maybe even a usb key, dvdr or cdr with a video of you explaining everything and telling the viewer who you are, what year it is, what's going on and what's important to you right now. Place it all in a water tight container, maybe even an iron case and weld it shut.
If you have small kids, tell them what you're doing and show them .... maybe they or their kids or your descendants might dig it up some day.
Of all the places I've renovated, I would have enjoyed finding something from someone else's life.