Ransack Deviantart.com for good Gimp tutorials :3
But for talk of this tag -
I honestly don't see anything that you can improve on in this particular piece. Typography, Christmas Colors, and scattered brushes there work nicely together as a simple sig. It's clean cut, which is good.
*For things you might want to experiment with;
Once you raid DA for tutorials, download a grip of brushes from different styles (round, pop, victorian, 70's, etc) and try fitting those into some of your work. It's an idea that may flow well into where you might want to try next.
Potential here's a milestone.
/V/