Create demoable UX

![newuserexperience](https://cloud.githubusercontent.com/assets/8646429/5345117/26975f54-7ee3-11e4-8fdf-e7e9be9465f8.gif)

This should use the image-url helper, which will automatically use the asset path. So:

1) Take the `.erb` off the end of this filename
2) Change this line to `background-image: image-url("maindonate.jpg")`

Do that for the other lines too.