like for example, one time i was browsing through some neofetch screenshots and i found out that a lot of them have anime or furry stuff as their wallpaper or profile picture, but they use linux.

younger me would’ve freaked out by the idea of having proprietary files, but i still enjoy linux. what do you think?? please

What should they use in order to not freak younger you? A screenshot of some lines from the kernel source code? A picture of Stallman and Torvalds tenderly embracing (quite unlikely)?

On my Debian and Mint computers, I have countryside pictures (I live in Paris, I miss seeing some real country landscape, mind you) and paintings (oil and watercolors, all works I admire) and some illustrations (comics, manga, whatever I appreciate enough to be wanting to look at it from time to time).

Sorry for younger you but I don't have a single image related to Linux nor to GNU philosophy, no matter how much I appreciate them.

freaked out by the idea of having proprietary files

I would suggest you read a little more about what the four essential freedoms are and how they relate to code and the user rights, not so much to do with art and wallpaper choice.