Hi Jean-Claude, I love what you have done with the Debian spiral in your proposal. It would be great to create a monochrome image which a background highlight color that users could easily chose – preferably by using a color picker in a theme setting menu.
But I would omit the squares. In my opinion most designs do to much and every Debian release I root for the minimalistic proposals. Most designs are just too distracting for my taste. It would feel more natural to me if it was just your improved spiral with only a rather understated logo as an optional feature. I was bold enough to adapt your initial proposal. I made the gradient bigger so that the screen is somewhat brighter: https://freidenk.net/debian/ Cheers Onsemeliot