Add in changing background image of main page header

Had a couple minutes during lunch, liked @jhanstra 's idea about changing images of the home page. So... I did that.

![image](https://cloud.githubusercontent.com/assets/3534544/5509193/3a093684-877b-11e4-8e5f-aaf27f5975d0.png)

![image](https://cloud.githubusercontent.com/assets/3534544/5509219/534d567a-877b-11e4-8ce0-d109493c3e42.png)

![image](https://cloud.githubusercontent.com/assets/3534544/5509207/4489a440-877b-11e4-9390-3cd85f251493.png)