Those are stickers!

I used to get them from sticker machines in the States back around when Pokémon came out in the early 00s. They cost US$.50 a piece and you got a random sticker from the series inside a cardboard protective sleeve. I used to have a bunch; slapped them on notebooks and such. Funnily enough, it was those stickers that got me interested in Japanese versions of Pokémon cards in the first place.
I actually would be interested in those (for nostalgia if not actual value), though I wouldn't assign all too much monetary value to them. Maybe $.50-1 a piece? More like a toss-in than anything else. Something to keep in mind for the future perhaps.