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.