Rachel, I can't speak for Metro, but my guess is that he'll say no because the things you bring back from time traveling are covered by other collections -- metals, gems, books, gnomes. The only exception is the picnic basket, and trying to collect 10 of those would be a lot of trouble. I seems to me that it would be like trying to make a collection of things you dig up with the miner, but again, Metro might have a different opinion.