First off thing is the render, you have stretched it and it looks bad. Try to sort that out. Next, you have kind of just spammed brushes for a background, try to make it out of effects or a stock. Now, the colour of brush you have used for your background don't go with your render, you should try to make the render and background match, the final result of the sig will be much better.
Just work on these things and post a 2nd version

Good Job :y: