Pacote de Temas para Ubuntu 16.04 Xenial

Ubuntu 16.04 Xenial Themes

MacBuntu OS (MBuntu) Transformation Pack for Ubuntu 16.04 Xenial Xerus New

Vivacious Color Themes	Yosembiance Smooth
Ubuntu 8.04 Theme (GTK)	Ambiance & Radiance Flat Colors (GTK)
Ambiance & Radiance Colors Suite (GTK)	Paper Gtk Theme
Arc Themes(GTK)	Ambiance Crunchy themes(GTK)
Ambiance Lime (GTK 3)	Flatabulous theme

Fonte:
http://www.noobslab.com/p/themes-icons.html