@ Kenneth
I am working on REST API support but it is far from being complete. Images can be added programmatically but there is no specific API to do so at the moment. You have to write the code to save the image into the connections-images folder and then update the data in the options column of the primary table. The next update of Connections will have a few methods in the cnImage class cnImage::download() this will retrieve an image from a URL as save it to an entry’s sub folder within the connections-images folder. cnImage::sideload() will allow you to move an image on the current web server to the correct entry folder. And, finally, cnImage::upload() which takes an $_FILE global to upload an image from a form submission.
Not sure it this helps, but I hope it does.
