The character in my pfp (assuming you mean them?) rn is meant to have a gothic feel, they're a character in a 1920s murder mystery project I'll likely never finish which is also what I'm looking for backgrounds for. I might take your advice on that, I feel those would work well paired with the sprite artwork.
Viewing post in AI assets are so annoying
Okay, here's what I could quickly find with free/cc0/fair-use/public-domain for 1920's style or gothic:
https://www.pexels.com/photo/shallow-focus-photo-of-black-wooden-open-door-at-th...
https://www.rawpixel.com/image/3289206/free-photo-image-window-arch-gothic-windo...
https://pixabay.com/photos/arch-gothic-architecture-building-899062/
https://pixabay.com/photos/arch-gothic-architecture-building-62929/
https://www.flickr.com/photos/132740829@N02/23678012302/
https://commons.wikimedia.org/wiki/File:Tombs_of_Emperor_Takakura_1920s.jpg
The website snappygoat.com seems to scan multiple sources. But you might need to search Pexels and/or Rawpixel directly.
A tip for legit copyright is the ability to see who actually made the content and a way to check their work. Even when attribution isn't required, it's helpful to keep record of where you obtained your media. In case someone tries to sue you, you have a paper trail defence. Especially if the person trying to sue you has no actual control over the material.