GTK themes
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Vertex. https://github.com/horst3180/Vertex-theme. Vertex is a theme for GTK 3, GTK 2, Gnome-Shell and Cinnamon. It supports GTK 3 and GTK 2 based desktop environments like Gnome, Cinnamon, Mate, XFCE, Budgie, Pantheon, etc.
Ceti 2. https://github.com/horst3180/Ceti-theme. The GTK3 theme supports Gnome 3.8, 3.10 and 3.12, but the Gnome Shell theme only works on 3.10 and 3.12.
Libra. http://gnome-look.org/content/show.php/Libra?content=167689. Light modern theme for Ubuntu or MATE.
VimixDark-Gtk-Themes. https://www.gnome-look.org/p/1013698/. Flat clean and dark theme for MATE and Ubuntu Unity.
Paper. https://snwh.org/paper/. Paper is a light and flat icon and theme set that is light and fast as well as good looking.
Yosembiance Theme. http://www.sundman.ca/themes/yosembiance/. Modified Ambiance theme that is less tacky than the default Ubuntu theme and would suit any Linux GTK desktop. Screenshot.
Android themes
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Numix Icons. https://play.google.com/store/apps/details?id=com.numix.icons_circle. High-resolution icon pack for Android devices.
Pixel 2040. http://imgur.com/a/3384a.
End of Evangelion. http://imgur.com/hdXEs4G.
Amoled Sith Lord theme. http://imgur.com/r/androidthemes/iCeKtft.
Praos icon pack for Android. https://plus.google.com/103259272253179703637/posts/ex2Qbt1p6QM. Lovely icon pack for your Android device.
Google wallpapers app. Get some awesome wallpapers on your Android phone. https://play.google.com/store/apps/details?id=com.google.android.apps.wallpaper.
Lines free icon pack. https://play.google.com/store/apps/details?id=com.natewren.linesfree&hl=en. Lovely icon pack for your Android device. Nova launcher required.
Nova launcher. https://play.google.com/store/apps/details?id=com.teslacoilsw.launcher&hl=en.
Wallpapers
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Dead space horizon wallpaper.
Shanghai city at night.
575 quality wallpapers for your Linux desktop. No watermarks.