This repository contains a copy of BeautyLine, which source does not seem to be published anywhere else.

In addition, it contains a customized version of it that adds status icons for WiFi, Bluetooth and Volume control. I performed this customization and I am currently using this theme in my NixOS machine.

You should be able to find this soon on Nixpkgs unstable under the attribute name beauty-line-icon-theme.

$ nix-shell -p gnome.gtk
$ gtk-update-icon-cache .

If it all goes well, you will see the following message.

gtk-update-icon-cache: Cache file created successfully.

If not, continue reading.

In most versions, there is a badly named file that causes the following error.

gtk-update-icon-cache: The generated cache was invalid.

Renaming it should fix the issue.

$ mv apps/scalable/goa-account-msn.svg\n.svg apps/scalable/goa-account-msn.svg

Though, it could be any other file name.

$ ls -a -R * > filenames
$ vim filenames

Once in Vim, use search and replace to discard symlinks.

:%s/ -> /***/g

Then replace white spaces.

:%s/ /@@@/g

Now searching for @@@ should hopefully point to the problematic (s) file (s).

$ mv apps/scalable/keysmith\ 1.svg apps/scalable/keysmith_1.svg