how many have you done before?
5/10 Assuming this isn't your first siggy
Your render is flatter than the assassin normally is that throws on an alarm
You need to find a tut and try to use a style from it you have to perhaps if you wanna be like me... use smudging, gradient maps, blurs, and sharpens
Also the background should look similar to the render you have to make the render blend, yet stick out, confusing i know