You think back to time Capsules, how many of you have been involved in one back at school, for the Millennium, or something else of a big event - so why not do one from your Wedding.
You can place in photos, videos and predictions for the future seal it up and then wait. Decide ahead of time how long you'll wait until you open it again -- your 10th anniversary? 25th anniversary?
Although most people equate "time capsule" with "something you bury in the ground," burying your wedding time capsule isn't a great idea. Not only does that subject the contents to extreme temperature variations, chances of you leaving behind a buried capsule before the hoped-for anniversary rolls around are high indeed. Instead, keep yours out of the elements and somewhere relatively kind -- avoid damp attics, but a climate-controlled closet would be just perfect.
Why not also get close friends and relatives in on the fun. Have them scribble up some predictions -- or perhaps marital advice. Take advantage of a pre-wedding party to snap photos of them and tuck the photos into the capsule.
While you're letting others in on the action, there are number of ways to go about it. One is to compose a list of predictions for everyone to guess at. For example, ask participants to predict:
How many children you'll have,
what kind of household robots you'll have,
how many career changes you've gone through,
what major nation we're closest to, and which one we're mad at,
what animal is the trendiest pet,
... and so on.
Another is to ask your wedding party and close friends to compose short letters to you. Give them each envelopes, and instruct them to tell you on the outside when it's time to open the envelope. Some will simply say "fifth anniversary," "10th anniversary," or "when your first child is born." Others will get more creative -- and you'll probably find it's terrific fun to stretch out the time capsule concept in this inventive, unpredictable way.