After a bit of digging looks like it was made by an artist named cierra who also made the packet hero background lol and a bunch of other maps like chloe, lost desire, breach, humanoid, image material, der wald, paradise, garakuta doll play, just to name the ones I recognized

Here's a link to the pixiv post but yeah a lot of osu map backgrounds were made by them lol 

https://www.pixiv.net/en/artworks/54180993