Congrats, you have done really great work here.
There are just two minor observations.
First, there's some kind of inconsistency in the normal maps (?). The first male character displays really outstanding foldings at arms and pants (little bit too much), whereas the details at the body looks quite flat (maybe it is just the lighting).
The second one is, that you should create a better show off of your character. Create a small plattform, pose your char, use some fancy camera perspective, choose the right background and atleast 3-point lighting to render your art more impressive. Eg. the dark train on a dark background is really hard to read. Just pimp your presentation to justify your great work.