You couldn't find it? Or did you just not take the time? I found it within 1 minute. Anyway, here is PewDiePie's Background for Amnesia created by: GhastDagger
To install this, go to the Amnesia root folder
C:\Program Files\Steam\steamapps\Common\Amnesia: The Dark Descent
Once you're in this folder, locate the 'main_menu' folder and in that folder click on 'main'
Copy and Paste the custom downloaded background and overwrite it. (Make sure you backup the original main_bg.map)
Once you're in the 'redist' folder, locate the map called 'main_menu' and in that folder select 'main'
Copy and paste the custom downloaded background and overwrite it. (Make sure you backup the original main_bg.map)
If you have (for any reason) accidently delete the original 'main_bg.map' you can get the original file here: