I think this is a really good start. I think to get more realism you need two things, better materials and more modelling.
For example, what is the blue material supposed to be? Will the owner of the house really want a Blue house like that, does the material have any kind of texture to it? reflection?
Secondly, it looks as if this is more of a massing model. When trying to create a realistic rendering you need to think in more realistic terms. How would the soffit inside your overhang attach to the walls, is there any trim around the fascia, walls etc. It almost needs to get to the point where you model it as if you were building it for real (almost).
And finally, if you look at 90% of the best realistic renderings out there I would say that 60% of it is modeling/rendering and 40% is post processing in Photoshop.
But yeah, very good start, just start looking around you at different building materials and see the texture, reflection, refraction, gloss, and connections to other materials. And then create you own Vray Materials to match it or model it in sketchup.
Hope this helps,
Rob
