Hello, i’ve found a little time so i modeled and rendered the iphone 6s, i hope you will like the image 
Comments and critics are welcome !
Cheers !
Nice image. The model looks very detailed and the lighting is quite good as well.
If you want to improve the render I would suggest you watch this great video about composition by Andrew Price if you haven’t already: https://www.youtube.com/watch?v=O8i7OKbWmRM
The composition of your image is not bad, but I think the two phones in the front are fighting for the viewers attention.