How do I Make a (NOT TILED) looping background?

Ok, I have a background THAT IS NOT tiled. It's a space background, and after about a minute or 2, it leaves the image into a white screen. How could I make it loop? Thanks!

All the code I have for it is :

System : Every Tick : Set scroll X to scrollx + 8* dt

Thanks!

The way I do it is to have two instances of the background right next to each other, which reposition themselves when they go past certain points. Here's an example:

Repeated Background Example

It works

Thanks