Hello,
@LovelyNorth and I have put together a visual guide to help you shop for furnishing items that are unlocked by completing achievements.
This guide was made to create an easy way to answer:
1) What items are available and what do they look like?
2) What achievements are needed to unlock them?
3) Where can I buy them?
If that sounds interesting to you please check it out at:
http://lovelynorth.com/achievementfurnishings/
Feel free to provide any comments or feedback!