Hm, simple but efficient.
It's up to you, really. Personally, I like more detail and work done in a signature, whereas I like my avatars to remain elegant and primarily simple. =)
The image and character as it is, is very nice though.
edit * now that I look at it, and actually concentrate ( try to understand, I can't see very clear right now, it's late and my eyes hurt, and other reasons as well ) I do notice something I'd definitely touch up. The character's hair made me realize how pixelated and etchy the image is... I'm thinking either it's just not truly high quality or you resized it, and I'm willing to bet you resized it. If you have PSP, you should resample ( I think that is what it's called, been a while though so I can't remember ) rather than resize. PSP usually preserves images, but resampling preserves a better and smoother look in the end if all else fails. So if you work on it more or get anybody else to do so, this is a touch up that'd make a reasonable difference in the overall presentation of the image. Also, borders always always always improve a signature's appearance. Why... is unknown.