A lot of people get hung up on finding art for their games, but that doesn't have to be the case! Just look at Hatoful Boyfriend.
If you know of any places to look up public domain or creative commons resources to use in games, please link them here!
200+ Free Art Books Are Now Available to Download from the Guggenheim
The New York Public Library wants devs to make games using its collections
Update:
A bunch of high-resolution photos under Creative Commons Zero ("do what you want") license are at Unsplash.
You can also check Flickr for images with the "Mods & Commercial Use Allowed" license option if you can give attribution to every asset, or "No Known Copyright Restrictions" license flag if you don't want the burden of keeping notes on sourcing/attribution.
Since these will mostly be photos not all of them will be suitable as backgrounds depending on your style, but since they're do-what-you-want or Modifications allowed, you can totally crop/filter/redraw/trace/whatever from them without any worries!
For audio you can look at Freesound.org (in search results, the little "person" icon means attribution required, versus a "0" icon which means no rights claimed.)
And then of course Archive.org has a bit of everything, which gives it a bit of a discoverability problem. But for something like music: if you can find a genre that fits your game, you'll probably have everything you need right there!
Opengameart.org has a tonne of free to use assets as well, including SFX and music.
Check the license, you will most likely have to credit the artist in your game or on your gamepage.
A quick search found these:
anime portraits
Backgrounds:
I just noticed that itch.io even allows Asset bundles to be uploaded! So maybe you'll have luck finding stuff there!
Better yet:
Game assets filtered by the 'visual novel' tag :P
https://itch.io/game-assets/ta...
Here's some assets that have caught my eye for whatever reason https://itch.io/c/165125/dev-a...
