This one is better for a few reasons, some of which I had decided not to go over last time. First off, the composition is better. The pony and the wand/magic aren't as disjointed, because the magic creates the illusion of being the tail. There's a better flow to the piece. The next thing I notice is that you were wiser in your choice of border. In the last version, the white border was distracting, but the blue border isn't.
Next I'm noticing that the same magic and pony that work well together, also clash. The style of artwork that the pony is in is different than the wand and magic effect. They should look as though they are one, whole cohesive image. When you have images from different sources/styles/mediums it "can" be difficult to create a cohesive look. It makes it look as though you just slapped some images on there without much consideration outside of positioning.
Maybe it's my screen, but your text looks a little blurry. I don't know what the reason for that might be (it could be so many things), so that's something you'll have to look into (if it is in fact blurry). The gradient you've added to the text and the sparkles make it more interesting than what you've had before. However, it's still kind of clumsy and bland. Adding text to signatures is something I struggle with myself, so I'm not entirely sure on how to help you out there. The best I can offer is to first experiment with the placement of the words, to create a pattern that will allow the eye to flow, or get real creative and find some different way of displaying your text. Again, various tuts out there will help you out with this.
Generally, if I'm making a signature that is very focused on an image, I add very little text, and I position it as close to my focal point as possible. My current signature is an example of what I'm talking about. The eye is easily drawn to text, so you don't want it to clash too strongly with your focal point. Decide if you want the text or the images to be the focal point, and then build around that.
I also use GIMP, although I would much rather use Photoshop. For various reasons, I cannot use Photoshop right now. You'll find signature tuts for GIMP lacking in comparison to tuts for Photoshop (I have in my experience anyway). If you know both programs well enough, then you can just use either kind of tut, and figure out the differences.
The one website I will direct you towards is
Abduzeedo. It's a general graphic design website, but it can give you a great deal of insight into how graphic design works (a great deal of the stuff on Abduzeedo is professional level). The various tuts provide great techniques, and looking at their various galleries and articles will allow you to acquire new ideas. I contribute a solid 80% of my growth in dabbling with graphics from this website.