One of my most favorite icons on GNOME has been Dropline Neu! for many years and I still have a copy of it since 2006. It is now hard to find.

Download ICON-DroplineNeu.tar.bz2

And, copy to /tmp directory

# cd /usr/share/icons
# tar xvfj /tmp/ICON-DroplineNeu.tar.bz2

Launch gnome-tweak-tool and select Neo Icons for your desktop.