The bg looks very messy looks like alot of liqufier was used, hmm try to create a not so messy bg and then blend in the render a bit more, also the blueish fog color over it doesnt fit the other colors, i suggest to remove all that. Also you need a light source try to take out a white soft brush, large and then click once where you want the light to come from, (keep most of the brush outsite the sig.