What do you mean with “the microflow returns json data”? Is the microflow returning a string? If so, it will not be easy.
If your microflow returns an object that contains a json string, you could associate an image object with it and show it in a nested dataview.
You need to use an import mapping to convert your JSON into an entity model. You can convert your image string into a file document type using CommunityCommons (Base64DecodeToFile I think). Return your root object to the page as a data view, and use the Image Viewer widget to display.