The DG Toolkit logo is based on this image form Wikimedia Commons:
Wikimedia Commons is an online repository of free-use images, sound, and other media files. It is a project of the Wikimedia Foundation. https://commons.wikimedia.org/wiki/File:Leaf_Simple_Green_L.svg
Favicon specific were generated using http://realfavicongenerator.net/
Insert the following code in the section of your pages:
<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
<link rel="icon" type="image/png" href="/favicon-32x32.png" sizes="32x32">
<link rel="icon" type="image/png" href="/favicon-16x16.png" sizes="16x16">
<link rel="manifest" href="/manifest.json">
<link rel="mask-icon" href="/safari-pinned-tab.svg" color="#4996f1">
<meta name="msapplication-TileColor" content="#ffffff">
<meta name="msapplication-TileImage" content="/mstile-144x144.png">
<meta name="theme-color" content="#ffffff">
And serve the content of the images/favicons directory from the root of your website.