GTK Themes.
Zukitwo: http://gnome-look.org/content/show.php/Zukitwo?content=140562. A very good GTK theme for Gnome Shell and MATE.
DeLorean-Dark — Gnome 3.4 & 3.6: http://gnome-look.org/content/show.php/DeLorean-Dark+–+Gnome+3.4+%26+3.6?content=153866.
DarkMint: http://gnome-look.org/content/show.php/DarkMint?content=150904.
Piratunbu theme 6.0: http://gnome-look.org/content/show.php/Piratunbu+full+theme+for+Ubuntu+13.10?content=147063. A pirate themed look for Ubuntu.
reNIX (for Unity and GS): http://gnome-look.org/content/show.php/reNIX+%28for+Unity+and+GS%29?content=153312. A squared theme for Unity and Gnome Shell.
Win2-7 Remix: http://gnome-look.org/content/show.php/Win2-7+Remix?content=153233. A Windows 7 styled theme for Unity and Gnome.
Elements: http://gnome-look.org/content/show.php/Elements?content=145920.
Wallpapers.
Tri screen space wallpaper with mountains and lovely nebula: http://media.moddb.com/images/groups/1/8/7872/wallpaper-1059063.jpg.
Tri screen milky way wallpaper: http://awesomewallpaper.files.wordpress.com/2012/05/the_milky_way_3375x6000_16x9_by_thyrring-d4vc2kl.png.
Awesome nebula wallpaper with lovely green color: http://www.redpepperwallpaper.com/wp_highres/space/WP4UNLED.jpg.
Super high-resolution wallpaper of a castle in Scotland: http://st.gdefon.com/wallpapers_original/wallpapers/543662_caerlaverock_castle_caerlaverock_dumfries_scotland_7359x4911_%28www.GdeFon.ru%29.jpg.
Quad screen wallpaper of Ayers Rock: http://fc05.deviantart.net/fs47/f/2012/040/c/5/simply_uluru_by_kouiskas-d27e3t7.jpg.
A Hong Kong wallpaper for 4 or more screens: http://st.gdefon.com/wallpapers_original/wallpapers/246505_gonkong_-panorama_-neboskryoby_-okean_9683x1600_%28www.GdeFon.ru%29.jpg.
Tri screen everest panorama: http://www.mountain7.com/wp-content/uploads/2009/08/everestpanorama.jpg.
Skyrim Dawnstar wallpaper: http://fc01.deviantart.net/fs71/f/2012/325/f/b/skyrim___dawnstar_wallpaper_by_xgv159-d5lrnc3.jpg.
Icon themes.
Plateau: http://sbstnblnd.deviantart.com/art/Plateau-0-2-391110900. A flat theme for MATE and Unity/Gnome Shell.
Just another Buuf Remix: http://gnome-look.org/content/show.php/Just+another+Buuf+Remix?content=135329.
MacUltimateLeopard: http://www.mediafire.com/download/lvmwl3iwr2y/MacUltimate_Leopard_2.4.tar.gz. A Mac OSX theme for Linux. Perfect for MATE.