Ubuntu 15.04 just released on 23rd, April and many themes designer are updating their themes to make them compatible with new version of Ubuntu which uses GTK 3.14 and Gnome Shell 3.14 by default, you can update Gnome Shell to latest version using PPA.
Ceti-2 is a theme designed for GTK-3, GTK-2, and Gnome Shell. It is dark theme with the white and blue combination based on Vertex theme which makes desktop more elegant. This theme is compatible with Unity, Gnome Shell, Gnome Classic, Gnome Fallback, Cinnamon, Mate, Budgie, Pantheon, and so on.
Vertex is a theme for GTK 3, GTK 2, Gnome-Shell and Cinnamon. It supports GTK 3 and GTK 2 based desktop environments like Unity, Gnome Shell, Gnome Classic, Gnome Fallback, Cinnamon, Mate, XFCE, Budgie, Pantheon, etc. Vertex theme comes with three variants to choose from. The default variant with dark header-bars, a light variant, and a dark variant.
Both themes uses same engine to render theme properly gnome-themes-standard package for GTK-3, Murrine and pixbuf engines for the GTK-2 theme. Since both themes are in active development, if you encounter any bug within these theme then report it to creator via linked page. Rave-X icons used in following screenshots. You can use Unity Tweak Tool, Gnome-tweak-tool or Ubuntu-Tweak to change themes/icons.
>> Available for Ubuntu 15.04 Vivid/14.10 Utopic/14.04 Trusty/Linux Mint 17.1/17/and other Ubuntu derivatives
To install Ceti(2) theme in Ubuntu/Linux Mint via PPA open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:
>> Available for Ubuntu 15.04 Vivid/14.10 Utopic/14.04 Trusty/Linux Mint 17.1/17/and other Ubuntu derivatives
To install Vertex theme in Ubuntu/Linux Mint via PPA open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal: