GNOME 3 (with GNOME Shell) is truly great and I especially like how easy it is to extend it through extensions like the new ThemeSelector extension.
ThemeSelector GNOME Shell extension is a new, unofficial GNOME Shell extension that adds a new tab in the Activities overview where all the GNOME Shell themes (not GTK themes!) installed under ~/.local/share/gnome-shell/themes show up. To change a theme, all you have to do is click it and you don’t even have to reload GNOME Shell.
To use the ThemeSelector extension, you need to install GNOME Shell Extensions and the GNOME Shell User Theme extension. But don’t worry, despite a first look on the installation steps below, installing all of these is actually quite easy. Read on!