Most people collect them in a binder, with pockets similar to pokemon card pockets. People who don't collect them put them in their phone cases, or put them on walls, corkboards, binder covers, etc.
Can you put photocards in your phone case?
Instead of having to remove your case and put your photocard, this way you can just slide it in! Decorate your case with stickers (stay tuned!) and more, including keychains through the keychain holes on the side of the case.