My daughter watches adverts, and like any other child who watches adverts, she sees toys and jingles and things get lodged in her head. She knows Lelly Kelly shoes, Unicorn Poop (sadly real) and loads more. She sees me and my wife collecting the odd Funko Pop and she wants them too. All of us like to get the occasional Lego minifig blind bag and hope it will be the one we want.
(very happy that I have a Wizard of Oz Scarecrow minifig on my desk now!)
So just a small thought: what would an in-RPG collectible look like? What would a world with elves and dwarves have that would be interesting and thematic? Why should someone care? (player and character)
It can't just be about "getting a better sword" or "finding the three Zanthar Crystals" or some kind of key that's in four bits. What, small, interesting, non-trivial things could there be?