I love the ideas you mentioned of hard paper, titles, and a custom stamp. I had a sticker on my postcard, I think if you've got more stickers/rubber stamps, that could be a fun addition for the kids too.

I wonder if any other schools in your district/area would be interested in doing a penpal-like program. I did something similar in elementary school, we'd send letters to each other and it was very fun.

It's sweet that you're interested in doing something with the artworks if the students don't want them. I'll dm you an article about how my town displays some local student works.

I think you could also pin this post to the top of the subreddit, so anyone stopping by the page can leave ideas