During certain events you can win special jewelry boxes for your desk. Select a jewelry box on your desk (next to the trophies) to open it.

When you open it you will see that it is divided into 3 sections:

Medals: this is where all of the medals you have earned for completing special events are kept.
Jewelry boxes: this is where you can see all of the jewelry boxes you have received. If you have 2 or more jewelry boxes, you can swap them out. Select a jewelry box, then press the Use button.
Gallery: you can find pictures of the event creatures you have banished or placated during special events here. You can get these pictures by completing certain event quests.