The Backrooms is a creepypasta concept of glitching into some sort of liminal space outside of space and time. The inspiration was most likely the liminal space aesthetic that had been gaining popularity around that time. The original post came from 4chan’s /x/ post by an anonymous user who posted this image along with a small creepypasta. Due to the anonymous nature of it, there is really no person who can be credited with creating the Backrooms so the concept is public domain.
As for this picture, last year the owner of Hobbtown USA in Oshkosh, Wisconsin, Bob Mazza held a fundraiser for repairs of the location and one of the promises was releasing some old photos he had, including the iconic one which was found on archives of his website from 2003 when they were doing renovations.
He released them into the public domain and posted all his pictures of the location from back then onto the Internet Archive, you can find all the images here
So you can use the images and concept however you like.
