Like most games nowadays, Pokémon Picross comes with a special Medal section. These medals are obtained through normal gameplay as you achieve certain conditions such as completion of stages and times abilities are used. You get notified of this in the stage but can access a medal list from the map.

There are 100 medals to collect and each medal will give you 3 Picrites for completion. In the Medal List, you can see medals that are close to being achievable, but some will be blacked out until you get the one before it in the list. If you haven't got it, it will be listed as a Mystery Medal and tell you the requirements.