In this image I wanted to create Fantasy-realistic high-class interior over the sky, therefore Fantasy and realistic mix between modeling, texturing and lighting is needed, so I decided to modeling almost all the main furniture/object as fantasy-shape, and for texture I mixed fantasy textures with realistic ones(photo texture) to create balance, and for lighting is realistic this way for adding balance in realistic (since modeling and texturing part has 50 percent of fantasy setting ).
Actually this part is rather simple since I made many copy for almost all object, also I used many modifiers(like ffd, wave, taper, etc) to create more fantasy feeling. This modeling part take about 1 million polygons( including for exterior background).
In this part I mixed my texture(fantasy) with realistic ones, I used about 60 different textures in this images, here is the screenshot of material editor I have used.
Lighting & Rendering
In this important part I have used 14 v-ray lights(in every window) and 2 direct lights for interior and used 1 v-ray light and 1 direct light for exterior background, in this scene I used many warm color for interior (such as orange, cream, and some yellow) and for the background I used cold colour(mainly blue) to capture contrast feeling of warm and cold between the interior and the background. Here is the shaded rendering of the image.
And then for the composition I combined interior and the background in photoshop by layer and doing some color correction, sharpen, glow, etc to enhance the image. Here is the final composition of the image.