Another tip is to make sure there are no blank parts of the sig. Your Rashad sig is nice, but at the top behind the Rashad renders, it's plain black. It gives it an "empty" feel. My favorite type of sigs are ones with 1 render of a fighter, with a sick background and sick text, or a 1 render of the fighter and a picture/render or two of him fighting faded into the background. Basically, try to make sure nothing feels empty, or make sure the background has something goin on. I had this exact same problem when I first started making sigs (I overlooked text, left things empty, kept my renders plain without any blending modes). It was D.P, Toxic, and a few other guys who gave me tips on these things, you can learn a lot if you ask questions.
These are all generic tips, and the more you practice, the more you will learn and understand. You are improivng fast, keep it up, buddy.