My Dandruff in a 1/2 liter water bottle
Because the future will suffer from a crippling lack of my dandruff lying all round the place. My dandruff is a non-renewable resource (not now, only after I am dead. Right now there is just too much of it - clogging up storm drains, mounds of the stuff needing to be shoveled off the driveway, blocking all the fire exits, etc. I really need this time capsule to hold a lot of this crud. Might need to rent a backhoe.)

The Eiffel Tower
The French are not really taking good care of it. It is leaning over to the side, people are always dropping two different sized stones from the top floor, and it is made of pizza (or is that the other one? Not sure, I get those two towers mixed up.). Anyway, the future may lack a leaning tower of pizza, so best be prepared. The French will hardly miss it, because they already have all those Pyramids and Nose-less Sphinxes to take care of.

Every time capsule in the world, including this one
Every time capsule in the whole world (including this one) should go into my time capsule. It may be difficult to design a time capsule that can contain itself, but I am not really a detail guy, I am more of an idea guy. I will just subcontract out the work to China. China knows how to make lots of elaborate containers, like my shoes, so a time capsule that can hold every time capsule in the world (including itself) will be a snap for those guys.
My time capsule will be like Noah's Arc, except full of time capsules, instead of smelly animals... ...unless people put smelly animals insides of their own time capsules... better pack a few brooms in their too, to sweep up the droppings.