I took it upon myself to fix the looping in Cethiel's otherwise superb desert background, and this is what I came up with. It also works well in a Pixel Art style, under the kind of restrictions that were common to hardware in the 16 bit era.

The original is here: https://opengameart.org/content/desert-background-0

There are foreground assets to go with it too: https://opengameart.org/content/desert-assets

Many thanks to Cethiel for posting the original under the most permissive license, meaning that I can post this version under the second-most permissive license. I guess I should also make clear that I use OGA-BY in the hope of making it easier for a creator who sees a derivative work to find the original - so a link to this post is fine for credit.