They're everywhere

[yankop]

Who is the creator/artist of images like these? I've seen them everywhere, on the character sorter, on YouTube videos, on memes etc. Also, is there any place where I can bulk download them?

[Flame Sniper]

They all come from this website. Idk about bulk downloading them.
https://tohosort.frelia.my/

[Maden]

Artists are alphes, kaoru and dairi as listed below in the touhou sort site. Different options for bulk downloading stuff. Personally I use Hydrus Network but it might or might not fit your overall use case as it does more than just download images.