For a lot of people, installing Linux is as much about finding an alternative to Windows as it is asserting some kind of identity:
That identity? Linux Bro. There's the surly penguin mascot:
The ever-so-slightly outdated pop culture references:
The "hacker" ideal:
The anime:
The... whatever this is:
There are thousands of terrible Linux-inspired wallpapers which, like most other parts of the operating system, were made by volunteers. It's a forgotten, and bizarre, part of nerd culture.
Check out the rest at Terrible Linux Wallpaper. Thanks to @slowdecade for finding this.