To ensure that all authers is known for each medie file. Only files that cannot include authers in the source are mentioned. 

Poul Sander's files are multi licensed under "GPL v2 or later" OR "CC-BY-SA any version"

/textures/
background_sixteen_nine.png  Poul Sander (based of qubodup's background.png)
fallback.png            Poul Sander
mouse.png               Poul Sander
gui_back_white.png      Derived from UI pack by Kenney Vleugels (www.kenney.nl) (CC0 license)
gui_back_yellow.png     Derived from UI pack by Kenney Vleugels (www.kenney.nl) (CC0 license)