I've spent considerable time looking for GTK3 themes that meet your requirements...

		nine_k on July 24, 2015 \| parent \| context \| favorite \| on: Firefox nightlies for Linux are now using Gtk+3 I've spent considerable time looking for GTK3 themes that meet your requirements. My current choice is openSuse-Pistachio which is green, reasonably compact, and did not break for two consecutive Ubuntu releases. zonColor icons work beautifully, too, with adjustable colors. There are a few more reasonable choices (though not oodles) on gnome-look.org

Thanks! I'll keep that in mind for when I run out of choices and have to upgrade :).