Overall, nice rendering. A few points (IMHO):
The people appear to have a white halo around them, and comparing them to the materials and the car, they look out of scale (too small).
The gray wall in the background looks flat, devoid of any texture - doesn't look realistic.
You have some light rays projecting from some of the top corners - why? It seems out of place in what looks like an otherwise photorealistic approach. If your going for a more mannerist style that emphasizes the form, you should use that approach on the whole form you want to emphasize.
Water seems a bit too agitated for a swimming pool.
