penguinmigrating.svg 
  originally drawn by Moini and published on openclipart.org:
  https://openclipart.org/people/Moini/penguinmigrating.svg

penguin_gliding.svg
  modification of penguinmigrating.svg by Klaas van Gend, march 2014.

  
monster truck.svg
  originally drawn by netalloy and published on openclipart.org:
  https://openclipart.org/detail/105607/monster-truck-by-netalloy
  
tuxkart.svg
  modification of monster truck.svg by Klaas van Gend, march 2014.

Milkman666_Cone_svg_1.svg
  originally drawn by Milkman666 and published on openclipart.org:
  https://openclipart.org/detail/10911/cone.svg-by-milkman666-10911 

stk-logo.png
  supertuxkart logo taken from http://stkaddons.net/
  presumed to be under a suitably free license

* steam-wheel.svg
   AUTHOR: Klaas van Gend
   License: PD
   Original graphics for The Butterfly Effect
   The images marked with an asterisk are uploaded to www.openclipart.org
