Since hiding questions using the body::esri:visible column is currently a beta feature, this post would be better placed on the Early Adopter forum. That way it could potentially be addressed before the body::esri:visible column is officially supported. This behaviour is because image and audio questions are actually attachments to the feature service, but is definitley a valid enhancement. Thanks for identifying this, I'll update the Early Adopter documentation to list it as a known limitation for now.
This blog seems to illustrate that image questions are supported under body::esri:visible but I am still seeing image questions when I try and use it on version 3.15 connect. Is this still not supported and is there a work around?
Amazing that years later ESRI still hasn't addressed this bug despite the functionality becoming standard.
You'll have to use the same solution we've all been using for 2 years - put the image into a group and hide the group.