Not quite sure but I believe it's pretty a unique thing in Switzerland: We use to have images printed on the lid of the small cream portions you get when ordering a coffee in a restaurant. The producers usually release series with 12 different images about a specific theme. A lot of people like to collect them and there are even yearly books with images of all the themes released within that year. It's a bit like post stamp collecting. Crazy!
As the current theme is about the Patrouille Suisse and there surely are some aviation enthusiasts around here I thought you might be interested in this
) but it's a lot more interesting than just a plain boring foil top.