Do you have the skills to self-host? If so, you can host any number of cloud storage services: Nextcloud, Immich, Cryptpad. You could even host a Forgejo instance (the software Codeberg runs on) although it's really not intended for storing the kind of images you're talking about.

I am guessing, though, that you are probably not a very technical person, and self-hosting might be out of the question for you. In which case unfortunately your options are a fair bit more limited. There are free hosted Nextcloud instances—Disroot hosts one. Or you could go with something like Proton Drive. If you're open to proprietary options then there's several very widely used options like Dropbox, Google Drive, Mediafire, etc. But if you're posting here, you probably don't want those.