Try getting a bit more random with the brush making, and while youre at it, with applying them too. I find the best way to learn how to use some elements of Photoshop is to get really random at first, and then work your way from there figuring out what achieved what, thus getting to know the program itself. The brushing, in this particular sig, is used in a very primitive manner. The sig itself is also very monotone in style, and in my opinion, doesnt deserve such big dimensions. Try cropping it, see how that goes.