As you play through the stages, you will find that completion of some of the challenges does not give you Picrites as you may expect but rather give you Mural slabs. These are pieces of a much larger image that can be completed, often referred to as Micross.
Each image is a 8x8 mural with each square being a 10x10 Picross puzzle. Each of these squares encompass a small part of the final image that can only be seen on completion. Mural pieces are only found within the Standard World.
There are two murals to complete, needing 128 different mural pieces and each mural has got a timer to show how long you have spent on the puzzles.
When the puzzles are complete, you have the ability to start them over all again in order to obtain a better score. You cannot use the Primal Reversion Pokémon as Support Pokémon.