Any Ubuntu MATE imagery likely taken from the official artwork pack
I'm having fun with Inkscape. It's been a long time since I've sat down and played with it. All of these are from scratch except for the logo and rondels.
If you play with the SVG file for the ones sporting grids, the grids are rendered as fairly complex paths. They make my laptop run crying from the room, so fair warning if it's a bit laggy trying to edit them on lower specc'ed machines
As you can tell, I like simple geometric shapes and a minimalist look, for the most part.
The source SVG files for all of these wallpapers can downloaded here from my Google Drive account
This one is special for Vivid Vervet