When you see a "pro" sig makes it look good?
What makes the sig pop??
What style do you prefer, does it really matter what style it is?
The biggest thing that i think makes a sig stand out and sets some sigs apart from other is mainly the time and effort you put into it. Any one can slap a render on a background and say done. It might even look ok but it isn't gonna get you a standing ovation. Thought time and planning make sigs great.
Coloring is a must and i don't mean just lots of colors or multi coloring.
What i mean is colors the work well togather and well with your render ( I am going to use the term render in place of focal point but i am not meaning a render).
The best ways i have seen to color are well to motion blur a copy of your render and than use that to color your background or create you whole sig in grey scale than use diffrent methodes to color it.
There is more to coloring that just nicely blended colors it must also have depth (the contrast between light and shadows) and some contrasting to it. Flat sigs are boring and don't catch the eye!
The less busy a backgriound is the better.
Texturing and detail are key to a good background. The background must also flow with the render.
Effects play a role in sig creation to. If you go crazy with them it can ruin a great sig. IMO
a little goes a long way.
Text boxes, patterens, stuff like that are good additions as long as they don't make the background to busy and are not over powering!
Lighting ok this is a must but i am not talking about the lens flair or Lighting effect plugin. Those are both very abrasive and leave a big white blotch. You can achive excellent lighting from other means. Good lighting in a sig is a must!!
Text well i disagree with Kenny for only one reason It is a sig...... Sigs are supsded to have text! It is what they were orginal designed for! It i sllike doing an oil pinting with water colors you really can't call it an oil paiting can you! The text must blend well and there are tons of ways to do this. The softer and more blended the better.
Now as for a render i do not belive this is a must. You do need how ever a focal point and you can achive it with out a render!
The very last thing is Detail..... Detail.... rember that word the little things you add in and blend and work on to add a finishing touch mean tons. The little details make or break a sig!