I don't feel the sig is complete yet. I still want to add more without ruining what I had going on under the sack boy. I want to do something else with the text too, but I have no idea what else to do. Some advice would be really appreciated.
Add a light source, some white-yellow brushing and/or go to filter>render>lightning effects and play with the settings, don't over-do it aswell as don't force the light source. If you look at the render it seems that the light is coming from the top-leftish direction...