Each piece required a higher level and therefore is some sort of sub-trophy for it encourages you to level up. If your Monster reaches level 22, the first piece will become available for you to buy. The last piece can be bought when you reach level 30. Every piece costs 125 Rox, making the complete cost a total of 1125 Rox.
It functions as a poster to decorate your wall with. You have to manually piece them together yourself as there is no connection trigger like in the Puzzle Game you get to play in Super Moshi Missions or Quests or at The Daily Growl.
Gather the pieces and put them together for a funny monster scene.