I'll comment on what I saw.
First ,the preview you submitted.
Tracing images is OK, if you do it properly.
Like , add moving stuff in the backgrounds so your city would look more alive.
For example headlights in the distance or planes flying by, the water moving, and so on.
The buildings look too bright to be in night-time , and so does the sky , make it close to pitchblack and add a tint over the buildings , should sort it out.
The scope was traced horribly , you should correct it , the outside shape is bad;
Also the decals on the lens are wrong , I can assume that the player won't be able to aim with it correctly , make sure to do something about it , I suggest making it look more like this:
http://www.airgunsofarizona.com/MTC/MTC%
20Optics%20Reticle.gif
Good luck with your project, looking forward for it , PM me when it's done or you have a demo ;)