Try this SO question: https://stackoverflow.com/questions/1801458/free-image-hosting-with-open-api
There are several possible options, but you are looking at creating your own connector for a text editor that should interact with the API, but having said that, for the most part, you will probably write a connector for the image loading anyway, or at least Searching for one that works, since most (free) RTEs do not provide built-in file and image upload functions.
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