http://gnome-look.org/content/show.php/GNOME+Shell%3A+Nord?content=142971. Nord Gnome Shell theme, now compatible with Gnome 3.6.
http://gnome-look.org/content/show.php/LittleBigMod_2nd?content=152088. LittleBigMod Gnome Shell 3.6 theme. A very good and sleek theme.
http://gnome-look.org/content/show.php/London+Smoke+-+Gnome-Shell?content=142426. London Smoke theme for Gnome Shell 3.4.
http://gnome-look.org/content/show.php/malys+-++GS?content=142262. Malys theme for Gnome Shell 3.4.1. Another quality theme for your Linux desktop.
http://gnome-look.org/content/show.php/Darkair+%28+3.4%2B3.6%2B3.8%2B3.9.2%29?content=156215. Darkair Gnome Shell theme. A theme with a lovely orange motif.
http://gnome-look.org/content/show.php/NovaShell?content=151522. NovaShell Gnome Shell theme. This looks a lot like the default Gnome Shell theme.
Zukitwo GTK 3 theme: http://gnome-look.org/content/show.php/Zukitwo?content=140562. This is a very high rated GTK theme for MATE and Gnome Shell. This would be very good for any Gnome Shell desktop.
Hope GTK 3 theme: http://gnome-look.org/content/show.php/Hope+gtk3?content=141491. Another lovely GTK 3 theme.
DeLorean Dark. A dark brushed metal theme for GTK 3: http://gnome-look.org/content/show.php/DeLorean-Dark+–+Gnome+3.4+%26+3.6?content=153866. If you want a nice dark theme for GTK 3.0; then this one will suit you just fine.
はじめまして。突然のコメント。失礼しました。