We are aware of this issue and apologize for the inconvenience.
In the next release this will be solved by adding the FileDocument as input parameter of the microflow. This FileDocument (or specialization) will be used to store the binary content from S3.
In this way you have to create a FileDocument (or Image) entity yourself and pass it as the input parameter of the GetObject microflow.
Thanks for asking your question on the forum. There are a few options here. As you already used the getObjectRequest, I assume that you already have the file content/image. If so, I would suggest to store the binary in an object which is a generalization of ‘Image’ instead of ‘FileDocument’. If you do this, you can use the default image viewer of Mendix.
The Image widget from the Marketplace also supports direct URL's. Previously, I saw an implementation in which the profile pictures were being shown via a signed URL. This will make your implementation a bit simpler and always up-to-date. The downside here is that you need to fetch the image each time it's being rendered. This can involve higher costs.
Hopefully, this helps!