I've been collecting beer caps for years. I used to put them on a cork board, but I wanted to design a more aesthetic beer cap holder.
My design is a tile style board. Tiles can be connected to each other. As your collection grows, you can easily expand the area of your board by adding a few more tiles.

Thanks for UXO who made edges and corners, in order to give a finished appearance.
https://www.thingiverse.com/thing:5205807