Wallpaper is customized version based on submission to Ubuntu 26.04 LTS competition for Resolute release set! I took the one without the logo and added my own smaller customized version of the logo, coloured green for MATE, and positioned it to look like a moonrise on Dune! 
BTW, the icon at the middle of the top panel,
is a launcher for hide/show all desktop icons (currently all hidden, because of the mess!!!)
If interested on how to do that, take a look here!