Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics
SalesBundles
Jobs
Tags

If you're using a public repository like GitLab or GitHub, you could create an Assets folder and put all the psd and png images in there. Don't bother about the base64, as that requires an extra step to decode it and it's in the source code anyway.

If you're not using a public repository, you could put the psd files in one zip file and the png files in another zip file and make those available somewhere, such as the downloads on your itch.io game page.

I could make it downloadable from the game.

I was debating base64 so that people wouldn't have to import and convert it themselves in the game. They could just copy and paste the asset and then place it where they wish. However, you're right, it's probably much easier to just have the png and they can place it where they want using their own image editor.