1. Face too dark, mask out whatever layer is above him where his face is
2. I would make the render a little bigger still, but the way it is now is fine too
3. I am not a fan of the font, cruise through dafont and grab some script fonts there to start with (like Mistral and Kinescope)
4. I would grab two colours (two of the orange, blue, and purple), and run with it. Three colours is uaully too much imo. You can put a gradient map of the two colours over either the stock, the render, or both, to make them all meld a little better.