Now that the default theme is made by the community (at least for 18.10) we could think about a method to repeat this. There is a “Free Culture Showcase” for the wallpapers where everyone can post wallpapers and the best ones will be included in the following ubuntu iteration. I was thinking about a possibility to do the same for themes. Yes, yes, i know: themes are much more complex as a holiday-picture and would need much more time. But please, lets think about this:
How about reviving the “Human Theme”? I don’t mean the exact look of it but maybe the philosophy of it. A theme for human beings. Do you remember those times?
So how could this work?
- It could be a contest repeated every two years for an LTS-version of Ubuntu. It should be started very early (1-2 years before the LTS comes out?) - so we would have enough time to finish the theme.
- Designers from all over the world would get the chance to present their vision of a new theme more precise: of a “human” theme.
- There should be clear rules of what they should present: a complete colour scheme, multiple mockups, limitations of gnome should be accepted (min, max, close should be on the right side and so on) - this should give a clear target
- Should the community choose democratic or should we have a jury (chosen by community?)?
- After finding a winner the coders could start building the theme and the rest of the community could report bugs and help testing. The designer should accompany the development.
Should the theme be the default theme? I know a lot would react very negative by this. Maybe for the start it could be a second theme that is included to ubuntu. Remember the dust-theme?
To make this work we would need enough time and very good publicity to make many designers interested. A few years ago the internet was full with ubuntu mockups which never got the attention they deserved:
https://www.deviantart.com/?section=&global=1&q=ubuntu+mockup
With a contest like this we could make ubuntu always look modern (even in 8 years 
), attract designers all over the world and give them the chance to make their talent public to millions of users.
If you are interested in this idea we had to clear some questions:
- How much time do we need for writing a theme?
- How much time would a new icon-theme take?
- What exact criteria do we need for a theme?
- Would Canonical allow/support this?
I would add questions and criteria when you give me some.
So, what do you think? This idea still needs a lot of refinement and should be seen a startpoint.