Pale Moon version of the Winstripe (Firefox 1.x) theme
Originally based on Fox 2 The Moon, some icons are taken from that theme if Winstripe does not have an equivalent.
Simply download the contents of the "src" folder and pack the contents into a .zip file. Then, rename the file to .xpi and drag into the browser.
You can grab the latest release either from the Releases section of this repository, or the Pale Moon Add-ons Site.