Works from the following authors have been reused within their explicit permissions' terms; all under a public domain, free-for-reuse, creative-commons or any other license compatible with our specific use-case:
Themify icons (http://themify.me/themify-icons) / Free for any purpose
atom (http://www.wpclipart.com/science/atoms_molecules/atom.png.html) / Public domain
Lightning Icon (https://openclipart.org/detail/26221/lightning-icon-by-anonymous) / Open clipart