Here’s a list that was compiled. In this, you can find a lot of background creators and their work. (But when using, be sure to credit where it is required.)
Like @schittwriter mentioned, @IndieEpisode and @biancahail have added some amazing backgrounds they edited, so you could check them out as well.
@IndieEpisode - Indie's Background & Overlay Thread
@biancahail - Bianca Hail's Background Edits Thread
@Tesbie28 also makes some awesome backgrounds. Here’s the link to her drive - https://drive.google.com/folderview?id=17aNUswCDXOQpFey822zCaCnIQxHZlF7H
And a website called Episode Life has a lot of helpful backgrounds - http://www.episodelife.com/
@amepisode and @wincyyellow make a lot of backgrounds that are used by lots of writers.
@amepisode - BG TERMS 17.05.2020.docx - Google Docs
@wincyyellow - Backgrounds & Overlays – Wincy Writes