Ok, I think a clean and rebuild of the whole project did the trick.

I always forget when I don't use it for sometimes. When something is doing weird with Qt you have to clean, qmake or rebuild to get everything in order.

I will tag this issue as solved !

First, look and feel is a very vague thing. You should try to find something concrete, such as that the image is too light, too contrasty or something.

I think you have not assigned a color table to the input image, which it should need just like the output image. But wouldn't the conversion have been done with that already...

@Donn
There's no way to loselessly convert 16 bit integers into 8 bit integers, so you can't use QImage to display your image without dropping some of the information. I advise to follow @SGaist's advice and research what OpenGL provides and if that will suit your needs.

PS.
Please don't post multiple times the same question! I see tree distinct instances of you asking the same thing over and over again in a few hours period.
http://forum.qt.io/topic/64650/display-2d-array-of-type-uint16-as-grayscale-image
http://forum.qt.io/topic/64657/display-uint16-image