There is no way u can tell if a picture was taken with a Canon or Nikon, sorry. The difference is not that huge like Nikon fanboys r telling themselves. Both cameras are good just choose the one that matches ur needs more than the other. Its quite simply actually....
Says the Canon fanboy with his 1100D!

..What are you even doing in this thread?
But seriously. I'm a happy owner of 5D3, 1DX and 8 L lenses, but even though I am heavily invested into Canon, I admit that Nikon has MUCH better sensor tech these days. I have used my Canon bodies side by side with the D800E, and the difference is like night and day, especially when shooting landscapes and other scenes with high contrast.
The resolution and dynamic range is nothing but amazing.
That said, I do preffer the ergonomics and handeling of Canon. And besides, Nikon has nothing on the Canon's TS-E lenses.