User blog comment:Wildoneshelper/Background image suggestion/@comment-3225604-20140111115340/@comment-4189499-20140115102420

You don't blur the image yourself, but in many image editors you can choose the size of the file you save, meaning that the program will do what it can itself to lower the quality of the image in a way which allows you to have the best image quality for the lowest file size. And when I say file size, I mean in kilobytes, not in pixel width. In fact, with the kinds of images you would probably be using which are more cartoonish, it would probably raise the file size if you blur the image. But don't take my word on that last point. Just fiddle with the save settings on whatever image editor you're using to make the background and see what happens.