Add new K1 block assets. Move common assets into a static/common_images folder

New background-transparent pretty things:

![image](https://cloud.githubusercontent.com/assets/206973/2848592/73788486-d0c1-11e3-8bba-77b0b7cf8f78.png)

![image](https://cloud.githubusercontent.com/assets/206973/2848596/8fc45912-d0c1-11e3-88a4-a4cc09e563db.png)