I think this would be a fun addition to the game and a great way to personalize your king even more. While exploring you could have a chance of finding the birthstone of that month. Then you’d be able to make them into decorations. So in February you have a high chance of finding amethyst.

January – Garnet
February – Amethyst
March – Aquamarine
April – Diamond
May – Emerald
June – Moonstone or Pearl
July – Ruby
August – Peridot
September – Sapphire
October - Opal
November – Citrine
December – Blue Topaz
Maybe there could be crowns or necklaces?

http://imgur.com/2AWVkL5

http://imgur.com/f6YMLED