Improvement of background image bg.png

I have improved the sharp pixels of the background image.


Here is a comparison of the old background image and my improved version:

![background-comparison](https://f.cloud.github.com/assets/4200435/1698244/345b371e-5f3b-11e3-8767-dd88eeb418e9.png)


Note the sharpness of icons and text in the new background. The old sharp pixels of the background texture were interfering with text a bit, so I change this for you and kept the same color.


The improved background image is here:

![bg](https://f.cloud.github.com/assets/4200435/1698246/59341c36-5f3b-11e3-8301-f071bb5759bb.png)


My version is still the same 75px X 75px as the old one, but much slimmer with 1.702 bytes.