something is weird with the lighting, I think that is the main thing to focus on (I'd say get that figured out first before doing any other improvements) I'm not familiar with UE4 but it looks like lightmap issues, maybe overlapping lightmap UV's, maybe too low texel resolution, not sure.. for example, the dark band/shadow…
@Simtone It's cirtainly a good start! Now, without seeing your reference theres not much I can say so I will assume the proportions of a "generic" head. The main issues I believe are located in the side view, specifically the ears and lips. From a side profile on average the upper lip is dominant, meaning it extrudes…