I did a clean install of Ubuntu Gnome today. I installed cinnamon and switched to it (I left gnome installed). I was customizing the theme, and all settings were taking effect immediately, but I can't change the icon theme. Even if I select a theme and logout and back in nothing changes. Also, if I close the theme window and reopen it, it still has the icon theme that I chose, but it has the icon from the default Adwaita displayed. I ran updates and restarted, and now there is no desktop background and the ctrl-alt-T shortcut for terminal isn't working. I have tried reinstalling cinnamon, and nothing changed. I am running Cinnamon 3.2.7 on Ubuntu Gnome 17.04.
tldr;
When I select a theme for icon in cinnamon nothing happens. I can change all of the other theme settings. After a reboot the desktop is black and some keyboard shortcuts don't work.
Best Answer
OK, so after much experimentation I found a workaround, and a more permanent solution.
The Workaround
There were multiple issues, with separate solutions.
To solve the issue of the background being dark, I had to switch from the gnome greeter to lightdm:
...and then select lightdm. Now Cinnamon used the background from the greeter, which could be changed with the lightdm GTK+ greeter settings tool. This is not ideal, but it works.
To change the icon theme, I had to use the gnome tweak tool. I don't know why, but that correctly changed the icon theme.
As for the default keyboard shortcuts, I had to add them again. Instead of using the built in 'launch terminal' shortcut, I had to make a custom shortcut that ran
gnome-terminal
. Not ideal, but it works.The Longer-Term Solution
I still don't know exactly which programs were causing these issues, but I figured that the cleaner the install I could do the better.
I reinstalled, this time with the minimal ubuntu installer. After that, I installed cinnamon, and enabled lightdm, using instructions from this answer.
in
/etc/default/grub
change the line:and finally run
This gave me a working cinnamon install on Ubuntu. To get a nicer and more configurable greeter, I also installed the lightdm GTK+ greeter, and settings tool.