I just made a treasury a little bit ago. Here is an example for all of you who are still confused. It is very simple.
Just had a thought: Wouldn't it be funny if I got myself on the front page with this treasury? lol. That would be ironic. Luckily for you, I put myself in it so I doubt it will even get looked at! lol. Its a good one though. Definitely evokes feelings of vintage summer picnics as the name says. Good luck!