It doesn't matter if every image is unique.What appears to my face,is that all texture parts are very similar.This set involves no work at all on design,and flow of the set.It doesn't contain any robot-like features.The use of only two colors doesn't help either.
I stress more on design because this set is too random for my taste,just a bunch of scrappy lines.
You can improve by finding a reference picture just for inspiration,for example,finding pictures of robots
You can do robot sets without shading,if you want a cartoon(with pen tool) clean look.But,for the set to shine you will need great focus on design of each texture,and how it will fit in the whole idea.Also,try decreasing clutter to a minimum.