Taken from http://tango.freedesktop.org/Tango_Icon_Library, version 0.8.90 / public domain:

- prefsFeatures.png (converted from preferences-system.svg)

https://openclipart.org/detail/35425/tango-desktop-peripherals / Tango Icon Library / public domain:

- prefsInput.png

https://commons.wikimedia.org/wiki/File:Input-gaming.svg / Tango Icon Library / public domain:

- prefsInputAxis.png (Button removed)

https://commons.wikimedia.org/wiki/File:Input-keyboard.svg / Tango Icon Library / public domain:

- prefsInputButtons.png

https://openclipart.org/detail/171015/laser-printer / public domain:

- prefs3DPrint.png

https://openclipart.org/detail/2281/information-icons-set-by-kuba / public domain:

- information-icons-error.png
- information-icons-question.png
- information-icons-info.png
- information-icons-warning.png

https://openclipart.org/detail/171382/cross-icon-by-zawertun-171382 / public domain:

- close.png

octoprint.png:
* Copyright Gina Häußge
* OctoPrint is a registered trademark owned by Gina Häußge.
* https://octoprint.org/trademark-rules
