I think I can sum up most of your sigs.
With each, I see too blurry of effects being crowded together, and poorly blended with an image. Your best strategy is to stick with one basic layout and work to keep it stable, trying to create admirable texture. Your sigs have a poor spray paint feel, a below average graffiti style, and beg for one solid to color define it. I also notice that you use very low appealling fonts, and that can kill a sig automatically.
Just keep experimenting in photoshop, it's the best way to improve by yourself. Tutorials can also help, but should only be a learning experience that calibrates your overall knowledge, and efficiency with photoshop.