He simply tells me the 3D doesn't looks as real as the 3D from his previous 3D vendor or as a simple photo he took with his iphone.
I think the use of a good background image plus a HDRI for reflections is the key in most scenes.
Maybe it is something about my setup or post-texhnique. Or he is just to picky in some ways and misses the amount of work which you have to put in very detailed models for such an image.
I put comments below the attachments.
The ones with the little to much blueish tint are the latest ones. I always use Pathtracing or in rare cases PMC.
The balcony image has been done with Octane 1.5 (HDRI).
The other,really good one, is made with Indigo Renderer and I think it uses a HDRI image too. I may be an image with an emtpy terrace and the contruction plus furniture placed in 3D there.
The last one with the winter-garden and all the furniture in, is supposed to be 3D too. Which I really can't believe.
Really would love to hear some suggestion in all directions.

At the moment I re-installed my old Maxwell Render License and see what I can do there because it offers more control with HDRI files and displacement. I really doubt it will do a big difference to Octane.