Easy Things to Mail Boyfriend?

My boyfriend and I are long distance for the summer. He’s working in another state at a youth camp, so we won’t see each other for three months and we only get to talk a couple days a week. I wanted to send him some small things throughout the summer. Letters of course, but sometimes I thought it would be nice to put some small things in. Do any of you have any ideas? I thought of painting a little encouraging picture, maybe a Polaroid of me or a printed picture of us together. What other ideas are small? I’m looking for things to either fit in a regular envelope or a larger bubble envelope, but not really looking to pay shipping on a big box.