Select our MainMenu GameObject from Anchor, and create a new sprite by navigating to NGUI | Create | Sprite, or press Alt + Shift + S.
Select the new Sprite GameObject from MainMenu and perform the following steps:
Rename it as
Set its Atlas type to our Game atlas.
Set its Sprite to our Space tiling sprite.
Set its Sprite Type parameter to Tiled.
Attach a Stretch component to it by navigating to Component | NGUI | UI:
Set its Style parameter to Both.
You may notice that we have ugly lines between each repetition of the Space sprite. That is simply because there is a 1-pixel-wide border on the sprite. We can easily correct this by reducing the sprite's border value of 1 pixel.
Select our Space GameObject from MainMenu, and click on the Edit button next to the Sprite field, as shown in the following screenshot...