The title explains it: The API works fine for showing the visuals in the report, but images are removed. It would be nice if images can be supported too.
Please can create/vote an idea in http://ideas.powerbi.com for your suggestion.
This one is similar to yours: https://ideas.powerbi.com/forums/265200-power-bi-ideas/suggestions/15120669-provide-powerbi-graph-as-image-on-request-similar
Best Regards,
Herbert