gilles, I believe you can already do this, if I am not mistaken. See my attachment. This is geared toward the Wrike Api (a project management software) but I believe it should work for any API. They needed a Base64 encoded image as well.
Set the body type to “Form-data” then the parameter gives you the option to add a value that is an image. Check off Send file and it should work! Note the content type I have in my header - octet-stream. That’s important as well. The other two items (X-File-Name and X-requested) I don’t think are important…
P.S. If you want to be able to dynamically add an image, uncheck Private.
P.S.S. I named my parameter key “data-binary” since that’s what Wrike recommended.
