Browsing through this section of the forum there are loads of ideas and examples of great wallpapers.
Usually when I am looking for a replacement wallpaper I tend to gravitate toward those with nice scenes like beech’s or mountain views.
However, on the more useful front it would be interesting to see a wallpaper which has useful information on it like keyboard shortcuts or linux commands. A cheatsheet wallpaper packed with useful commands possibly interwoven with a nice beech or mountain scene emblazened with the Manjaro logo/name would be both very cool and useful to many. Perhaps a wallpaper detailing the full functionality of pacman would be a useful resource too.
Of course you can extend the above to include language syntax for all kinds of programming languages. You could then rotate these wallpapers on a time schedule to provide a kind of slideshow.
Just some thoughts and suggestions there for some more utilitarian desktop backgrounds.