Hey Chris,
You may use the Beans Image API with any images as long as you have the url for it. Check this discussion in which we speak about editing an image using the image url.
For post images, Beans as a nice shortcut function beans_edit_post_attachment(). It is similar to beans_edit_image() but instead of passing the image url as the first argument, you pass the post id and it will find and edit the post image for you. Note that beans_edit_post_attachment() returns an array and not only the url 😉
Happy coding,