First things first. Try to work with the render, not against it. Meaning: don't just put a render than a BG, they should be as one. So work off the render and use it to give you ideas to use in your sig. (Colors, effect, the kind of depth).
2nd. You want to keep your effects close to the render to make only one focal point. It is very hard to make a good sig with multiple focal points. So keep you effects complimenting the render and near to it enough to not distract the viewer from the focal.
We'll just start with that and we'll see where you go. Keep 'em comin' zero. Keep 'em comin'.