For some reason despite surfaces being at different angles the illustration looks very flat and there seems to be some confusion over the light source, some of the elements are in shadow but are still casting a shadow.
Also as I have said before the paint chips on the edges look very unnatural. Instead of using the sharp edged shape again and again, try painting something new each time, it may take a little longer but would make a big difference, have a look at real tanks and how they weather around the edges as it will help a lot.