Comment 25 for bug 24280

But is this easily fixed, or is this more of an architectual problem?
If its an architectual problem and the obvious solutions lead to security issues, the most obvious hack would be to enable a graphical way to install themes system-wide.

There is a graphical tool called gnome-art. It seems to be unmaintained though.
Perhaps some of the code there can merge with the appearance applet in the future.

A simple show filter that lets us choose between 'installed', 'available' could do the trick.
Another more ubuntu-way approach would be, to make the add button open up add/remove and add the 100 most popular themes to the ubuntu repositories automatically using some script.

That last solution would make the most sense, because some of these themes depend on gtk-engines not installed by default. It would be the same sort of solution as has been implemented within firefox.

With that scenarion, all we would need is a 'install more themes' button in the appearance window.
Off course the themes should get some sort of .desktop files to make them available in add/remove