a very good and easy to use file storage is AWS S3. There is a module in Make that can be used to upload the file and easily access it. Normally, when the S3 bucket is configured correctly, you can access the files through your own domain/url. You need to setup S3 bucket though.
I use Dropbox for my personal projects. I store files there and use the triggers to upload images (and other files) to Shopify or other related services in order to automate image provisioning.