Back to the FAQ…
A lot of people's answers would recommend a hosting provider that is not made for handling a lot of images at a time for a plurality, and happen to block Simply Plural and other services from using them. The simple reason is because they aren't made for that purpose and want to avoid server overload.
This is where Scratch Upload comes in; it is made for plurals and is made by a system. It is made accessible and has many privacy features.
Just create an account (or use the Dropbox), upload your images and copy their link (or even directly the Markdown format) to paste in any supported fields!
For more information about it, we have it listed in our project already!