One of my favorite things about receiving packages from individuals, rather than from mail order companies, is that I get to see stamps that often don't make their way onto envelopes and into my mailbox. For example, the above picture shows two $1 "Wisdom" stamps. I don't know their story, but I think they're magnificent.
And in this picture, there is a cartoon collection that would be difficult to find on an envelope, given their denominations.
Ephemera like this makes me happy. I love being able to find joy in the details.