Bluecurve for GTK3
Bluecurve is the GTK theme introduced in Red Hat 8 and used up until Clearlooks replaced it. It is a very clean old-school UI.
This is currently a work in progress. The goal is to provide GTK2 and GTK3 themes to bring Bluecurve into the 2010s.
The base of the GTK3 half of this theme is OneStepBack, a simple theme written from scratch that imitates the NeXTSTEP look. I picked this as a basis because most of the elements appeared to have similar geometry (especially in terms of solid rectangular borders).
See the Installing page in the wiki.
Summary: the Bluecurve engine is required for the GTK2 half. You must install
this separately. After installing the Bluecurve engine, simply drop this tree
into ~/.themes/Blueshell/
Blueshell is a contraction of Bluecurve and GNOME Shell (although there is an additional allusion to the blue shell of Mario Kart fame).