Windows 8, Microsoft’s latest operating system comes with a brand new Start Screen with modern interface and live tiles. Microsoft has replaced that old start menu with a new Start Screen in Windows 8. There are many options available to customize this Start Screen, such as, you can pin any program/folder to Start Screen, change the way tiles are displayed, and change the background image and accent colors. There is a functionality offered to change the background in the Start Screen in Windows 8, but the problem is that there is no way the user can select a custom background and the user needs to select one from available options only.
Fortunately, there is a solution to adding custom backgrounds in the Start Screen. ModernBack changer is a freeware program for Windows 8 that allows users to set custom backgrounds for the Start Screen.
The Background tab allows users to select the Start Screen background from predefined ones, or you can also select your own custom image. There is also an option to Restore the default image. It’s a good idea to use a light-colored image so that the icons in Start Screen can be easily viewed.
The Accent tab allows users to change the accent color for the start screen. You will need to log off your PC in order for the settings to take effect.
No doubt this is a workaround and Windows 8 should include this option to set a custom background. But since there is no such option, you can use ModernBack Changer. Get it from below link.