I'm not going to nitpick at your signature although you asked for criticism. That's because there are a lot of things that GFX artists already know is slightly off about their pieces of work. I honestly don't really feel that you need me to tell you every single detail that can be adjusted to make the composition slightly more appealing. For most part, I'm sure you're smart enough to find out yourself.
Overall, I enjoy your layout of the signature. However, I will make slight comments that may not be so obvious. When I first looked at it, I thought the sprites were a little too desaturated. Seeing as how they are in the foreground, you want them to pop up a little more than the background. You want to establish planes because of the way you positioned the sprites.
The pure black design you used in the middle throws off the color scheme of the signature. I understand you did not want to pick a color too close to the colors already used in your signature because that would cause confusion in differentiating the background from the foreground. However, I think you can pull off using a better choice than pure black. Black is a very strong color that stands out particularly in signatures such as this one. Our eyes divert almost immediately to the black in the background. (Similarly, the same goes for the border as well.)
In the end, I congratulate your efforts. I believe that good ideas are important. Art is a talent, but also a practice. Nothing comes without struggle. Good artwork can be produced with much practice, but ideas are a result of experience and observation.