How do I loop my scrolling background image?

I have a background of some vector clouds. I want them to continuously move to the left, with no jump when they reach the farmost right edge and go back to scroll the beginning.

How do I do this? I looked at Kirupa’s continuously scrolling image, but it doesn’t behave the way I want it to - it involves fading the image out at the end so you don’t notice the gap.

I want something more like this:

But without the randomly-generated clips, or the responsiveness to the mouse.

Do you understand what I’m saying?

This was done a lot a few years ago, but it seems the ONLY tutorial available is the one Kirupa made which doesn’t involve ActionScript (what I’m envisioning, would, I’m just not sure what).

If you have any suggestions, I would greatly appreciate them.